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1.
Summary An analysis of the allometric relations of the total volumes occupied by prolactin (PRL) and corticotropic (ACTH) cells (PRL volume and ACTH volume, respectively) to body length and a study of the immunocytochemical staining intensity of PRL and ACTH cells were used to determine the differences in activity of PRL and ACTH cells in freshwater-reared and in saltwater-reared Cynolebias whitei during the entire lifespan of this annual cyprinodont fish. An inflection in the allometric relation of PRL volume to body length was observed in fish of one-week old. The relatively large PRL volume in younger fish may be related to PRL cell activity before hatching. No inflections were observed in the allometric relations of PRL volume and ACTH volume to body length at the onset of maturation and the onset of ageing, indicating that the increased pituitary growth in maturing and ageing C. whitei is not the result of changes in PRL or ACTH cells. The slope of the allometric relation of PRL volume to body length in freshwater-reared fish was significantly steeper than the slope in saltwater-reared fish. The PRL volume in adult freshwater-reared fish was eight times larger than that in saltwater-reared fish of the same length. The intensity of immunocytochemical staining of saltwater PRL cells was significantly reduced. These volumetric and staining differences correspond to the low functional demand put upon PRL cells in saltwater-adapted fish. In contrast, the slope of the allometric relation of ACTH volume to body length and the intensity of immunocytochemical staining of ACTH cells were similar in freshwater-reared and in saltwater-reared fish. It is concluded that the functional demand put upon ACTH cells is similar in freshwater-reared and saltwater-reared C. whitei; the involvement of ACTH cells in the osmoregulation of the fish in both environments is similar. 相似文献
2.
Effects of changes in environmental calcium on prolactin secretion in Japanese eel,Anguilla japonica
E. Arakawa S. Hasegawa T. Kaneko T. Hirano 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1993,163(2):99-106
Effects of changes in environmental Ca2+ on the secretion of prolactin, a possible hypercalcemic hormone, were examined both in vivo and in vitro in the Japanese ecl, Anguilla japonica. Transfer of seawater- or freshwater-adapted fish to fresh water, fresh water containing 10 mmol Ca2+ · 1-1 sea water, Ca2+-free sea water, or deionized water was accompanied by significant changes in plasma Ca2+ levels after 7 days, except for the fish transferred from fresh water to fresh water and from sea water to sea water. Changes in external Ca2+ concentrations did not affect plasma prolactin levels, although plasma prolactin levels as well as pituitary prolactin contents were significantly greater in fish in a hypotonic environment than those in a hypertonic environment, regardless of the external Ca2+ concentration. Hypercalcemia, induced by removal of the corpuscles of Stannius, did not alter plasma prolactin levles. Incubation of the pituitary in the medium with different Ca2+ concentrations (up to 2.9 mmol·l-1) did not affect the basal release of prolactin, except at an extremely low Ca2+ concentration (less than 0.1 mmol·l-1) where prolactin release was inhibited. Addition of Ca2+ ionophore (A23187) to the medium led to a marked and significant increase in prolactin release, indicating that an increase in intracellular Ca2+ stimulates prolactin release. However, the effect was not specific to prolactin cells; a similar increase was seen in growth hormone release. These results indicate that changes in environmental Ca2+ concentration may not be the primary factor influencing prolactin secretion in the eel; changes in environmental osmolality or Na+ levels seem to be more critical for the regulation of prolactin secretion.Abbreviations CSX
stanniectomy
- DMSO
dimethylsulphoxide
- DW
deionized water
- FW
fresh water
- GH
growth hormone
- PRL
prolactin
- SW
sea water 相似文献
3.
K. J. Brewer B. A. McKeown 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1980,140(3):217-225
Summary Parr and smolt sea water acclimated coho salmon,Oncorhynchus kisutch were subjected to gradual and direct transfers to fresh water. Plasma osmotic pressure, Na+, K+, Ca++ and Mg++ were similar in freshwater (FW) fish and seawater (SW) transferred controls for the 24 h following transfer. In spite of the similarity in osmotic pressure and ion levels, plasma cortisol concentrations were significantly increased immediately following salinity change while both pituitary and plasma prolactin decreased indicating enhanced secretion by the pituitary and clearance from the blood. In vitro experiments showed greater incorporation of tritiated leucine into prolactin (PRL) cells immediately after transfer to FW while prolactin injections into intact fish lowered activity in rostral pars distalis (RPD) cells as measured by the same technique, providing evidence of hormonal feedback. These experiments show that the increased synthesis and release of PRL that occurs in coho following movement into FW is not obviously correlated with plasma osmotic pressure, Na+ or Ca++ concentrations as has been observed in other species of teleosts.Abbreviations
FW
freshwater
-
SW
seawater
-
PRL
prolactin
-
RPD
rostral pars distalis 相似文献
4.
Summary Prolactin (PRL) cells were studied electron-microscopically and morphometrically in the annual cyprinodont fish, Cynolebias whitei during its life cycle. In prehatching larvae, PRL cells possessed small secretory granules, giant mitochondria and a well-developed Golgi apparatus. During hatching, no changes were observed in the volume density of the secretory granules, indicating that no increased release of PRL occurs at hatching. A significant change in the composition of PRL cells, i.e., the volume densities per cytoplasm volume of the different organelles, occurred between one day and one week of age. Thereafter, only minor differences were observed between age groups, indicating that no major changes occur in PRL cell activity during the lifespan of C. whitei. However, the volume density per cell volume of the nucleus decreased steadily with age during the lifespan. A comparison of the PRL cells in young and adult fish reared in fresh water (FW) with siblings reared from hatching in diluted sea water (1/3 SW) did not reveal any differences with respect to the volume densities of the organelles, including the secretory granules. However, significant differences were observed with respect to the diameter, electron-dense content and affinity to anti- PRL serum of the secretory granules. These differences indicate that, despite the similar volumetric composition of the PRL cells, their secretory granules contain a substantially higher concentration of PRL in FW-reared fish than in 1/3 SW-reared fish. 相似文献
5.
Dr. Madeleine Olivereau Christian Aimar Jean-Michel Olivereau 《Cell and tissue research》1980,208(3):389-404
Summary The cytological responses of the pituitary gland during adaptation to deionized water (DW) were investigated in the goldfish and the eel. In both teleost species, a stimulation of the prolactin (PRL) cells could not be detected, although the levels of blood electrolytes (Na+,Ca2+,Cl–) are reduced in the eel. PRL cells appear less active in DW-adapted eels. A striking stimulation of the PAS-positive cells of the pars intermedia occurs in both species after 3 weeks and, in the eel, is still present after 11 weeks. Cell and nuclear hypertrophy, mitoses and a well-developed endoplasmic reticulum are observed. MSH cells are partially degranulated when pigmentation is affected; a reduced activity of MSH cells is evident after 11 weeks. The amount of neurohypophysial tissue is reduced. In the goldfish and the eel, during adaptation to DW, an unknown factor secreted by the PAS-positive cells of the pars intermedia appears to play a more important role than the secretion of PRL. These two species are able to survive in fresh water without the pituitary. The control of the PAS-positive cells by external sodium or calcium is discussed. 相似文献
6.
Pituitaries were collected from a common carp,yprinss carpi, belonging to vitellogenic phase and cells were disaggregated by using 0.3% collagenase and 0.05% tsypsin. Enzymatically
dispersed cells were incubatedin vitro in Ca2+-free medium to observe the effect ofCanna punctatus GnRH (cGnRH) and Ca2+ on pituitary cell cAMP accumulation. Addition of cGnRH (20 Big) to pituitary cell incubation (6 × 104 cells/well) containing 4 mM theophylline, a phosphodiesterase inhibitor, caused two-fold increase of cAMP accumulation in
comparison to control, Addition of Ca2+ (2 mM) to cGnRH further augmented cAMP accumulation, i.e., four-fold as compared to control. Increasing concentrations of
cGnRH in the presence of Ca2+ resulted in a dose-dependent increase in cAMP accumulation. To examine the specificity of Ca2+ augmentory effect on cGnRH-stimulated pituitary cell cAMP accumulation, a specific Ca2+-channel blocker, verapamil was used, At 3 μM dose verapamil completely waived Ca2+-augmentation of cGnRH stimulatory effect on cAMP. Interestingly, verapamil also significantly inhibited cGnRH stimulation
of cAMP in the Ca2+-free medium. Extent of Ca2+ plus cGnRH stimulatory effect on cAMP was further increased by the addition of 25 pmol of calmodulin, a Ca2+-carrier protein, Addition of verapamil to this system strongly inhibited Ca2+ and ealmodulin augnientory effect on cGnRH. Reduced level of cAMP in the pituitary cell due to verapamil was even lower than
that of cGnRH plus ealmodulin incubation. Data indicates a contamination of Ca2+ in an apparently Ca2+-free medium, Results suggest that in lower vertebrate, i.e., fish, GnRH stimulation of pituitary cell cAMP is dependent on
extracellulnr Ca2+ and incubation of pituitary cell in Ca2+-free medium is truly not free of Ca2+. 相似文献
7.
Seale AP Richman NH Hirano T Cooke I Grau EG 《American journal of physiology. Cell physiology》2003,284(5):C1290-C1296
Prolactin (PRL) playsa central role in the freshwater osmoregulation of teleost fish,including the tilapia (Oreochromis mossambicus). Consistentwith this action, PRL release from the tilapia pituitary increases asextracellular osmolality is reduced both in vitro and in vivo.Dispersed tilapia PRL cells were incubated in a perfusion chamber thatallowed simultaneous measurements of cell volume and PRL release.Intracellular Ca2+ concentrations were measured from fura2-loaded PRL cells treated in a similar way. Gadolinium(Gd3+), known to block stretch-activated cation channels,inhibited hyposmotically induced PRL release in a dose-related mannerwithout preventing cell swelling. Nifedipine, an L-typeCa2+ channel blocker, did not prevent the increase in PRLrelease during hyposmotic stimulation. A high, depolarizingconcentration of KCl induced a transient and marked increase ofintracellular Ca2+ and release of PRL but did not preventthe rise in intracellular Ca2+ and PRL release evoked byexposure to hyposmotic medium. These findings suggest that a decreasein extracellular osmolality stimulates PRL release through the openingof stretch-activated ion channels, which allow extracellularCa2+ to enter the cell when it swells. 相似文献
8.
In cultured rat pituitary tumour cells (GH3 cells) the absence of extracellular Ca++ or addition of NaEGTA reduced spontaneous prolactin (PRL) release and abolished the stimulatory effect of thyroliberin (TRH). Readdition of CaCl2, but not of equimolar concentrations of MgCl2 increased spontaneous hormone release, and restored the effect of TRH. The calcium ionophore, A-23187, induced PRL release during normal calcium conditions, but not when an excess NaEGTA was present. TRH increased cyclic AMP accumulation in the presence and the absence of extracellular calcium. The effect of TRH on PRL release and cyclic AMP formation occured concomitantly with an increased efflux of 45Ca2+. Intracellular electrophysiological recordings from the same single cells before and after TRH activation showed increased frequency and duration of the Ca2+ dependent action potentials. We conclude that TRH elevates the Ca2+ influx which depends on the depolarizing action current, and this effect is probably linked to formation of cyclic AMP and PRL release. 相似文献
9.
Leanna Jamieson Angel Waters Kaitlyn E. Ho Harvey Y. S. Chan Jacky T. Hung Sarah E. Webb Ching Man Chan Alan M. Shipley John G. Williamson Jon Beer Chevonne Angus Andrew L. Miller 《Journal of fish biology》2021,98(1):17-32
The elasmoid scales of anadromous sea trout Salmo trutta L. represent a significant internal reservoir of Ca2+. Although more is known about long-term remodelling of scales in response to calciotropic challenges encountered during smoltification and migration, very little is known about the contribution made by scales to the short-term, minute-to-minute regulation of Ca2+ homeostasis in the extracellular fluid (ECF) during these phases of the life cycle. This gap in the knowledge is partly due to the technical challenges involved in measuring small Ca2+ fluxes around the scales of live fish in real time. Here, this study describes exfoliating, mounting and culturing scales and their resident cells from parr, smolt and adult sea trout from a freshwater environment, as well as from adult sea trout caught in sea or brackish water. All the scales were then examined using an extracellular, non-invasive, surface-scanning Ca2+-sensitive microelectrode. The authors quantified the Ca2+ fluxes, in the absence of any systemic or local regulators, into and out of scales on both the episquamal and hyposquamal sides under different extracellular calcemic challenges set to mimic a variety of ECF-Ca2+ concentrations. Scales from the life-cycle stages as well as from adult fish taken from sea, brackish or fresh water all showed a consistent efflux or influx of Ca2+ under hypo- or hypercalcemic conditions, respectively. What were considered to be isocalcemic conditions resulted in minimal flux of Ca2+ in either direction, or in the case of adult scales, a consistent but small influx. Indeed, adult scales appeared to display the largest flux densities in either direction. These new data extend the current understanding of the role played by fish scales in the short-term, minute-to-minute homeostatic regulation of ECF-Ca2+ concentration, and are similar to those recently reported from zebrafish Danio rerio scales. This suggests that this short-term regulatory response might be a common feature of teleost scales. 相似文献
10.
Faggio C Torre A Pelle E Raffa F Villari V Trischitta F 《Comparative biochemistry and physiology. Part A, Molecular & integrative physiology》2011,158(1):143-149
The response of isolated hepatocytes of Sparus aurata to hypotonic shock was studied by the aid of videometric and light scattering methods. The isolated cells exposed to a rapid change (from 370 to 260 mOsm/kg) of the osmolarity of the bathing solution swelled but thereafter underwent a decrease of cell volume tending to recovery the original size. This homeostatic response RVD (regulatory volume decrease) was inhibited in the absence of extracellular Ca2+ and in the presence of TMB8, an inhibitor of Ca2+ release from intracellular stores. It is likely that Ca2+ entry through verapamil sensitive Ca2+-channels, probably leading to a release of Ca2+ from intracellular stores, is responsible for RVD since the blocker impaired the ability of the cell to recover its volume after the hypotonic shock. RVD tests performed in the presence of various inhibitors of different transport mechanisms, such as BaCl2, quinine, glybenclamide and bumetanide as well as in the presence of a KCl activator, NEM, led us to suggest that the recovery of cell volume in hypotonic solution is accomplished by an efflux of K+ and Cl? through conductive pathways paralleled by the operation of the KCl cotransport, followed by an obliged water efflux from the cells. 相似文献
11.
The dopamine receptor antagonist pimozide, at concentrations up to 10 nM, competitively antagonized the inhibitory action of a pomorphine on prolactin (PRL) secretion by cultured rat pituitary cells. At higher concentrations pimozide as well as the analogues clopimozide and penfluridol suppressed PRL secretion. The latter effect could not be reversed by dopamine antagonists devoid of intrinsic effects on PRL release. Suppression of PRL release was also observed with compounds which were devoid of dopamine receptor agonistic or antagonistic properties such as R 6694 and R 5052, structurally related to pimozide, and also with loperamide. The inhibitory action of pimozide on PRL release resembled that of the calcium antagonist flunarizine. Concentration effect curves showed parallel slopes and the effect of both compounds could be reversed by increasing the concentration of calcium ions (Ca2+). Both flunarizine and pimozide were also capable of inhibiting releasing factor-stimulated luteinizing hormone secretion, an effect not shared by apomorphine. Pimozide and the various structurally related compounds used, also antagonized Ca2+-induced smooth muscle contractions of the isolated caudal artery of the rat.The present findings indicate that pimozide is a competitive antagonist without partial agonistic activity on apomorphine-sensitive dopamine receptors in the pituitary and that its inhibitory effect on PRL release as well as on vascular smooth muscle contractions is due to interference with a Ca2+-dependent mechanism of the stimulus-effect coupling process. 相似文献
12.
Toshihiro Wada Masato Aritaki 《Journal of experimental marine biology and ecology》2004,308(1):113-126
Low-salinity adaptability was investigated in a flatfish spotted halibut Verasper variegatus during the period from late metamorphic larvae to early juveniles by a 20-day rearing experiment under different salinity regimes (1, 4, 8, 16 and 32 ppt). Effects of low-salinity on growth and development were examined and the changes in the prolactin (PRL) production level in the pituitary and the gill chloride cell morphology were examined as physiological backgrounds for low salinity adaptation. PRL cells and chloride cells were identified by immunocytochemistry with a specific antiserum for PRL188 and Na+,K+-ATPase. Most of the fish exposed to over 4 ppt survived for 20 days, but all the fish exposed to 1 ppt died within 5 days. Fish kept in intermediate salinities (8, 16 ppt) grew significantly better than those in the control group (32 ppt). Fish exposed to 4 ppt attained almost the same body length as the control group at 20 days after transfer, although these fish showed an abnormally dark body color as well as delayed development. These results suggested that spotted halibut has a high-adaptability to low-salinity environments and prefers an intermediate salinity near iso-osmolality (about 12 ppt) from the late metamorphic larval stage, but does not completely adapt to a hypoosmotic of 4 ppt salinity or less than half of the osmolality. The percentage of PRL-cell volume to pituitary volume was significantly higher at 4 ppt than in the control group. The chloride cells in gill filaments were significantly larger at 4 ppt than in the control group. These results suggest that juveniles could adapt to a low-salinity environment due to the activation of PRL production and enlargement of chloride cells. These laboratory findings suggest that late metamorphic larvae and early juveniles of spotted halibut may utilize a low salinity environment such as estuarine tidal flats or very shallow coastal areas as their nursery grounds in the sea. 相似文献
13.
Humic substances and the water calcium content change the toxicity of malachite green 总被引:1,自引:0,他引:1
T. Meinelt M. Pietrock A. Wienke F. Völker 《Zeitschrift fur angewandte Ichthyologie》2003,19(6):380-382
Laboratory experiments were conducted to test interactive effects of calcium (Ca2+) content and the presence of humic substance (HS) on malachite green (MAG)‐induced toxicity in fish embryos and larvae by means of a semistatic 144‐h‐embryo‐larval‐test with zebrafish (Danio rerio). Two kinds of reconstituted water samples were used to produce the test media by mixing salts into deionized water resulting in either hard water (↑Ca ? HS), or soft water (↓Ca ? HS). By adding HS two additional test media were produced (↑Ca + HS, ↓Ca + HS). MAG was tested in concentrations of 0.05, 0.10, 0.15, 0.20, 0.25 mg L?1. The toxicity ranking of MAG (mg L?1) to embryos based on 96‐h‐LC50 in the different test water samples is: ↑Ca ? HS (0.061) > ↑Ca + HS (0.123) = ↓Ca ? HS (0.12) ≥ ↓Ca + HS (0.134) and on 144‐h‐LC50 to larvae is: ↑Ca ? HS (0.038) > ↑Ca + HS (0.06) > ↓Ca ? HS (0.077) = ↓Ca + HS (0.077). Mortality of all the groups was significantly different (P < 0.05). Increased Ca2+ concentrations did not protect zebrafish embryos and larvae from MAG‐induced toxicity. At high Ca2+ conditions, the mortality of the embryos as well as of the larvae is reduced in the ↑Ca + HS group relative to the ↑Ca ? HS group. Thus, at high Ca2+ conditions the HS does affect the MAG‐induced mortality. The mechanism which causes the higher toxicity of MAG in the presence of higher Ca2+ concentrations is poorly understood. A probable explanation could be the stimulation of the calcium‐binding protein calmodulin as well as the calmodulin kinase II in cell membranes in the presence of high Ca2+ concentrations. 相似文献
14.
A. A. Maksimovich V. M. Serkov E. O. Zagal’skaya A. A. Kudra 《Journal of Evolutionary Biochemistry and Physiology》2000,36(3):334-345
The morphological and morphometrical changes in the renal proximal tubular cells of the salmonOncorhynchus gorbuscha during spawning migration are described for the first time. The evaluation of the ultrastructural changes in the kidney of
the adult humpback salmon allows concluding that the proximal tubular cells are affected by significant osmotic loads during
spawning migration. Various destructive processes in the proximal tubular cells indicate a decrease of their functional activity
in the fresh water. The analysis of the results of the study of the humpback salmon kidney ultrastructure during the anadromous
migration allow suggesting that reduction of the amount of the most active cell organelles in the proximal tubule, such as
mitochondria and the basolateral membrane system, is associated with a decrease of the number of ion pumps that operate less
intensively in the fresh water. Such mechanism of the kidney functioning in the euryhaline fish appears to be formed in the
course of evolution as an adaptation to the freshwater environment. The morphological and morphometrical changes in the proximal
tubules of nephrons were described for the first time in Pacific salmon smoltsOncorhynchus keta, O. gorbuscha,O. Kisutch, andO. masou in environments with different salinity. The most marked response to the transfer to the sea water or to the calcium-enriched
sea water was observed in the chum salmon smolts. In 48 h, the tubular diameter reached its peak, more than 72 μm, the tubular
lumen also was very large, while the epithelium height was only slightly greater than that in the fresh water control. In
spite of the considerable morphological changes, as soon as in 24 h (the Ca2+-enriched sea water) and in 48 h (the sea water) the ion content in smolt carcasses was within the physiological norm for
the environment with enhanced salinity. These results indicate a high efficiency of the osmoregulatory system in smolts during
their transfer from the fresh to the sea water. 相似文献
15.
Dr. Haruo Nogami Damon C. Herbert William B. Winborn Frank J. Weaker Peter J. Sheridan 《Cell and tissue research》1987,248(1):75-78
Summary Nuclear uptake and retention of3H-estradiol by luteinizing hormone (LH) and prolactin (PRL) cells was examined in three species of rodents (guinea pigs, hamsters and gerbils) using the combined techniques of immunocyto-chemistry and autoradiography. Castrated animals were injected with3H-estradiol and decapitated 1.5 h later. The pituitary glands were processed for thaw-mount autoradiography followed by conventional immunocytochemical staining for LH and PRL.3H-estradiol accumulated in more than 80% of the anterior pituitary cells in the gerbils, while only 33 and 22% of the cells accumulated3H-estradiol in the hamsters and guinea pigs, respectively. A varying percentage of immunoreactive LH and PRL cells in all three species were found also to contain binding sites for estradiol. Some LH and PRL cells in hamsters and guinea pigs and only some in PRL cells of gerbils were found to be devoid of grains. Quantitative analysis revealed that the number of grains per nucleus differed considerably from cell to cell. LH cells of guinea pigs accumulated much larger amounts of3H-estradiol than did the PRL cells, while the LH cells in the hamsters and gerbils accumulated only slightly more3H-estradiol than the PRL cells.These results confirm the previous observations in rats and baboons that demonstrated tremendous species differences in percentage of cells in the anterior pituitary gland that accumulated3H-estradiol. Also, these data suggest that there are functionally heterogeneous cell types among the LH and PRL cells in hamsters, guinea pigs and gerbils as has been previously demonstrated in rats and baboons. 相似文献
16.
N. C. Guérineau P. M. Lledo D. Verrier J. M. Israel 《Cell biology and toxicology》1994,10(5-6):311-316
Prolactin (PRL) release and intracellular free calcium concentration [Ca2+]i were measured in two populations of normal rat lactotrophs (light and heavy fractions) in culture. Spontaneous PRL release of heavy fraction cells was more sensitive to dihydropyridines (DHPs; Bay K 8644 and nifedipine) when compared to the light fraction lactotrophs. The stimulatory effect of thyrotropin-releasing hormone (TRH) on PRL release from heavy fraction cells was inhibited by Cd2+ and mimicked by Bay K 8644. Indo-1 experiments revealed that TRH-increased [Ca2+]i was reversibly inhibited by Cd2+. In a Ca2+-free EGTA-containing medium, TRH did not modify [Ca2+]i.Abbreviations [Ca2+]i
intracellular free calcium concentration
- DA
dopamine
- DHP
dihydropyridine(s)
- DMEM
Dulbecco's Modified Eagle's Medium
- Ins(1,4,5)P3
inositol 1,4,5-trisphosphate
- PRL
prolactin
- RIA
radioimmunoassay
- TRH
thyrotropin-releasing hormone
- VGCC
voltage-gated calcium channel 相似文献
17.
Background
Estradiol (E2) mediates various intracellular signaling cascades from the plasma membrane via several estrogen receptors (ERs). The pituitary is an estrogen-responsive tissue, and we have previously reported that E2 can activate mitogen-activated protein kinases (MAPKs) such as ERK1/2 and JNK1/2/3 in the membrane ERα (mERα)-enriched GH3/B6/F10 rat pituitary tumor cell line. Phytoestrogens are compounds found in plants and foods such as soybeans, alfalfa sprouts, and red grapes. They are structurally similar to E2 and share a similar mechanism of action through their binding to ERs. Phytoestrogens bind to nuclear ERs with a much lower affinity and therefore are less potent in mediating genomic responses. However, little is known about their ability to act via mERs to mediate nongenomic effects.Methods
To investigate the activation of different nongenomic pathways, and determine the involvement of mERα, we measured prolactin (PRL) release by radio-immunoassay, MAPK activations (ERK1/2 and JNK1/2/3) via a quantitative plate immunoassay, and intracellular [Ca2+] by Fura-2 fluorescence imaging in cells treated with E2 or four different phytoestrogens (coumestrol, daidzein, genistein, and trans-resveratrol).Results
Coumesterol and daidzein increased PRL release similar to E2 in GH3/B6/F10 cells, while genistein and trans-resveratrol had no effect. All of these compounds except genistein activated ERK1/2 signaling at 1–10 picomolar concentrations; JNK 1/2/3 was activated by all compounds at a 100 nanomolar concentration. All compounds also caused rapid Ca2+ uptake, though in unique dose-dependent Ca2+ response patterns for several aspects of this response. A subclone of GH3 cells expressing low levels of mERα (GH3/B6/D9) did not respond to any phytoestrogen treatments for any of these responses, suggesting that these nongenomic effects were mediated via mERα.Conclusion
Phytoestrogens were much more potent in mediating these nongenomic responses (activation of MAPKs, PRL release, and increased intracellular [Ca2+]) via mERα than was previously reported for genomic responses. The unique non-monotonic dose responses and variant signaling patterns caused by E2 and all tested phytoestrogens suggest that complex and multiple signaling pathways or binding partners could be involved. By activating these different nongenomic signaling pathways, phytoestrogens could have significant physiological consequences for pituitary cell functions. 相似文献18.
Kinetics of sodium (Na+) and calcium (Ca2+) uptake were studied in cardinal tetras Paracheirodon axelrodi acclimated to humic substances (HS, 35 mg C l?1) and low pH (pH 3·72), parallel to analysis of whole body Na+ and Ca2+ content. This species had a high uptake capacity (Jmax) for both Na+ and Ca2+ in soft, ion‐poor water. The affinity constant (Km) did not vary significantly among treatments for either Na+ or Ca2+. Jmax Na+ increased 30% in fish acclimated to HS for 5 weeks. Acclimation to low pH had no effect on Jmax Na+ but this treatment was associated with a 32% decrease on whole body Na+ content, suggesting that fish were unable to compensate for the increased Na+ loss induced by extreme acidity. Exposure of fish to HS + low pH, the treatment most closely approximating to the conditions experienced by the species in its native environment, resulted in an increase in whole body Na+ by 31% relative to acclimation to low pH alone. Jmax Ca2+ in cardinal tetras was high relative to that documented in other freshwater species acclimated to soft water (Jmax= 30 nmol g?1 h?1). Prolonged exposure of fish to pH 3·72 inhibited Jmax Ca2+ by 53%, although whole body Ca2+ content remained unchanged relative to control. Acclimation of fish to HS + low pH resulted in an increase of Jmax Ca2+ by 166% relative to low pH alone. Collectively, these results suggest that HS protect cardinal tetras acclimated to soft, acidic waters by preventing excessive Na+ loss (as indicated by whole body Na+ content) and by stimulating Ca2+ uptake (as indicated by increased Jmax Ca2+) to ensure proper homeostasis. 相似文献
19.
Seale AP Richman NH Hirano T Cooke I Grau EG 《American journal of physiology. Cell physiology》2003,284(5):C1280-C1289
In thetilapia (Oreochromis mossambicus), as in many euryhalineteleost fish, prolactin (PRL) plays a central role in freshwater adaptation, acting on osmoregulatory surfaces to reduce ion and waterpermeability and increase solute retention. Consistent with theseactions, PRL release is stimulated as extracellular osmolality isreduced both in vivo and in vitro. In the current experiments, aperfusion system utilizing dispersed PRL cells was developed forpermitting the simultaneous measurement of cell volume and PRL release.Intracellular Ca2+ was monitored using fura 2-loaded cellsunder the same conditions. When PRL cells were exposed to hyposmoticmedium, an increase in PRL cell volume preceded the increase in PRLrelease. Cell volume increased in proportion to decreases of 15 and30% in osmolality. However, regulatory volume decrease was clearlyseen only after a 30% reduction. The hyposmotically induced PRLrelease was sharply reduced in Ca2+-deleted hyposmoticmedium, although cell volume changes were identical to those observedin normal hyposmotic medium. In most cells, a rise in intracellularCa2+ concentration ([Ca2+]i)during hyposmotic stimulation was dependent on the availability ofextracellular Ca2+, although small transient increases in[Ca2+]i were sometimes observed uponintroduction of Ca2+-deleted media of the same or reducedosmolality. These results indicate that an increase in cell size is acritical step in the transduction of an osmotic signal into PRL releaseand that the hyposmotically induced increase in PRL release is greatlydependent on extracellular Ca2+. 相似文献
20.
W. S. Marshall S. E. Bryson J. S. Burghardt P. M. Verbost 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1995,165(4):268-277
We examined transepithelial transport of Ca2+ across the isolated opercular epithelium of the euryhaline killifish adapted to fresh water. The opercular epithelium, mounted in vitro with saline on the serosal side and fresh water (0.1 mmol·l–1 Ca2+) bathing the mucosal side, actively transported Ca2+ in the uptake direction; net flux averaged 20–30 nmol·cm–2·h–1. The rate of Ca2+ uptake varied linearly with the density of mitochondria-rich cells in the preparations. Ca2+ uptake was saturable, apparent K
1/2 of 0.348 mmol·l–1, indicative of a multistep transcellular pathway. Ca2+ uptake was inhibited partially by apically added 0.1 mmol·l–1 La3+ and 1.0 mmol·l–1 Mg2+. Addition of dibutyryl-cyclic adenosine monophosphate (0.5 mmol·l–1)+0.1 mmol·l–1 3-isobutyl-l-methylxanthine inhibited Ca2+ uptake by 54%, but epinephrine, clonidine and isoproterenol were without effect. Agents that increase intracellular Ca2+, thapsigargin (1.0 mol·l–1, serosal side), ionomycin (1.0 mol·l–1, serosal side) and the calmodulin blocker trifluoperazine (50 mol·l–1, mucosal side) all partially inhibited Ca2+ uptake. In contrast, apically added ionomycin increased mucosal to serosal unidirectional Ca2+ flux, indicating Ca2+ entry across the apical membrane is rate limiting in the transport. Verapamil (10–100 mol·l–1, mucosal side), a Ca2+ channel blocker, had no effect. Results are consistent with a model of Ca2+ uptake by mitochondria rich cells that involves passive Ca2+ entry across the apical membrane via verapamil-insensitive Ca2+ channels, intracellular complexing of Ca2+ by calmodulin and basolateral exit via an active transport process. Increases in intracellular Ca2+ invoke a downregulation of transcellular Ca2+ transport, implicating Ca2+ as a homeostatic mediator of its own transport.Abbreviations
DASPEI
2-(4-dimethylaminostyryl)-N-ethylpyridinium iodide
-
db-cAMP
dibutyryl-cyclic adenosine monophosphate
-
FW
fresh water
-
G
t
transepithelial conductance
-
I
sc
short-circuit current
-
IBMX
3-isobutyl-1-methylxanthine
-
SW
sea water
-
TFP
trifluoperazine
-
V
t
transepithelial potential 相似文献