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1.
Kazunori Takano Akihiro Takemura Mitsuru Furihata Teruyuki Nakanishi Akihiko Hara 《Environmental Biology of Fishes》1991,30(1-2):39-48
Synopsis Changes in serum steroid hormones were studied during the reproductive cycle of a viviparous rockfish,Sebastiscus marmoratus. Serum levels of estradiol-17β (E2) and testosterone (T) were moderately high throughout the spawning period from December until February (E2), and until post-spawning in April (T). Serum progesterone (prog) fluctuated but remained low throughout the annual reproductive
cycle; 17α,20β-dihydroxy-4-pregnen-3-one (17α, 20β-diOHprog), on the other hand, was relatively high during the spawning period.
During the spawning period, 7 of 12 females reared under laboratory conditions spawned twice at 10-to 16-day intervals. Histological
observations indicated that oocytes developed gradually during gestation of the preceding brood and; after parturition, developed
more quickly towards the end of vitellogenesis and subsequent fertilization. In repeat spawners, E2 and female-specific serum proteins remained high several days after the first parturition, then gradually decreased. Prog
showed no significant changes over the period. The 17α, 20β-diOHprog, however, was low immediately after parturition, then
rapidly increased, remained elevated during the middle of the period and then decreased. These results indicate that E2 is involved in vitellogenesis, and 17α, 20β-diOHprog may have some important roles in gestation in the multiple spawnerS. marmoratus. 相似文献
2.
Hamid Reza Jamalzadeh Saeed Hajirezaee Samane Nazeri Hossein Khara Elham Mirrasuli 《Biologia》2012,67(4):796-799
To identify a simple indicator for detection of follicular vitellogenesis stage of cultured Caspian brown trout, the changes of plasma calcium and estradiol-17β along with ovarian histology were investigated over a reproductive cycle. For this purpose, the blood and gonad samples were taken monthly over a six months period. According to results, the concentrations of plasma calcium increased significantly during October and November but then declined steadily until the end of experiment. Estradiol-17β concentrations were low throughout the experiment, a clear peak was observed in October. Histological observations showed that all examined females were in vitellogenesis when the peak of plasma calcium and estradiol-17β were observed. Also, significant positive relationship was found between plasma calcium and estradiol. The good fitness of plasma calcium and estradiol-17β peak with histological observations suggests that plasma calcium could be a good and simple indicator for detection of follicular vitellogenesis stage in the cultured Caspian brown trout. 相似文献
3.
P2X1 receptors, the major subtype of P2X receptors in the vascular smooth muscle, are essential for α,β-methylene adenosine 5′-triphosphate
(α,β-MeATP)-induced vasoconstriction. However, relative physiological significance of P2X1 receptor-regulated vasoconstriction in the different types of arteries in the rat is not clear as compared with α1-adrenoceptor-regulated vasoconstriction. In the present study, we found that vasoconstrictive responses to noncumulative
administration of α,β-MeATP in the rat isolated mesenteric arteries were significantly smaller than those to single concentration
administration of α,β-MeATP. Therefore, we firstly reported the characteristic of α,β-MeATP-regulated vasoconstrictions in
rat tail, internal carotid, pulmonary, mesenteric arteries, and aorta using single concentration administration of α,β-MeATP.
The rank order of maximal vasoconstrictions for α,β-MeATP (E
max·α,β-MeATP) was the same as that of maximal vasoconstrictions for noradrenaline (E
max·NA) in the internal carotid, pulmonary, mesenteric arteries, and aorta. Moreover, the value of (E
max·α,β-MeATP/E
max·KCl)/(E
max·NA/E
max·KCl) was 0.4 in each of the four arteries, but it was 0.8 in the tail artery. In conclusion, P2X1 receptor-mediated vasoconstrictions are equally important in rat internal carotid, pulmonary, mesenteric arteries, and aorta,
but much greater in the tail artery, suggesting its special role in physiological function. 相似文献
4.
Steroids both in seminal fluid (SF) and blood serum (BS) as well as the milt quality (sperm motility and sperm production)
were investigated during final maturation of Persian sturgeon. The BS levels of testosterone (T), 11-Ketotestosterone (11-KT),
progesterone (P), 17α,20β,21-trihydroxy-4-pregnen-3-one (20βS), cortisol (C) and 17α,hydroxyprogesterone (OHP) elevated after pituitary preparation (PP) treatment and then decreased during stripping period
for spermiating males. Such elevations did not occur for non-spermiating individuals and steroids remained in basal levels
after PP treatment until the end of stripping period. For both groups (spermiating and non-spermiating fish), the BS levels
of 17α,20β-dihydroxy-4-pregnen-3-one (DHP) did not show significant changes during experiment. During stripping period, the values of
all tested steroids were significantly lower in SF than in BS of spermiating males. SF levels of 20βS and 11-KT showed a decreasing trend and the other steroids were unchanged during this period. Significant positive correlations
were found between the values of 20βs and 11-KT in BS with their levels in SF. Also, BS and SF levels of 20βs and 11-KT were positively correlated with sperm motility characteristics (percentage and duration of motility) and sperm
production (sperm density and milt volume), respectively. The results showed the probable involvement of 20βs, P, OHP, T, 11-KT and C in final maturation of Persian sturgeon, especially 20βs and 11-KT had good correlations with qualitative parameters of milt. The lower levels of steroids in SF than those in BS
might also be essential for viability of Persian sturgeon spermatozoa. Probably, there are mechanisms that stabilize the concentrations
of a number of hormones in the SF. 相似文献
5.
Plasma Sex Steroid Levels and Steroidogenesis in the Gonad of the Self-fertilizing Fish Rivulus marmoratus 总被引:1,自引:0,他引:1
Masako Minamimoto Yoshitaka Sakakura Kiyoshi Soyano Yoshiaki Akaba Atsushi Hagiwara 《Environmental Biology of Fishes》2006,75(2):159-166
Synopsis The mangrove killifish, Rivulus marmoratus, is the only known self-fertilizing vertebrate. This species is sexually dimorphic; sexually mature individuals are either
hermaphrodite or primary and secondary males. Although the mangrove killifish has a unique reproductive strategy, there has
been no study on the reproductive endocrinology of this species. Thus we investigated plasma sex steroid hormone levels and
steroidogenesis in the gonads of R. marmoratus by enzyme linked immunosorbent assay (ELISA). Plasma 17β-estradiol (E2) and 11-ketotestosterone (11-KT) were detected both
in hermaphrodite and in primary male. Ovarian follicles (follicle-enclosed oocytes) from hermaphrodites, which were categorized
into early yolk stage and late yolk stage, and testis tissue of primary males were cultured with different concentrations
of 17α-hydroxyprogesterone (OHP) or testosterone (T) for 24 h. Production of T, E2, 11-KT and 17α-20 β-dihydroxy-4-pregnen-3-one
(17α,20β-P) in the medium from tissue culture were measured by ELISA. Early and late ovarian follicles of hermaphrodites and
testis pieces of primary males synchronously secreted E2, 11-KT, and 17α,20β-P following incubation with OHP or T. We conclude
that both hermaphrodite and primary male of the mangrove killifish secrete estrogen, androgen, and progestin synchronously. 相似文献
6.
Nickel ions have been reported to exhibit differential effects on distinct subtypes of voltage-activated calcium channels.
To more precisely determine the effects of nickel, we have investigated the action of nickel on four classes of cloned neuronal
calcium channels (α1A, α1B, α1C, and α1E) transiently expressed in Xenopus oocytes. Nickel caused two major effects: (i) block detected as a reduction of the maximum slope conductance and (ii) a shift
in the current-voltage relation towards more depolarized potentials which was paralleled by a decrease in the slope of the
activation-curve. Block followed 1:1 kinetics and was most pronounced for α1C, followed by α1E > α1A > α1B channels. In contrast, the change in activation-gating was most dramatic with α1E, with the remaining channel subtypes significantly less affected. The current-voltage shift was well described by a simple
model in which nickel binding to a saturable site resulted in altered gating behavior. The affinity for both the blocking
site and the putative gating site were reduced with increasing concentration of external permeant ion. Replacement of barium
with calcium reduced both the degree of nickel block and the maximal effect on gating for α1A channels, but increased the nickel blocking affinity for α1E channels. The coexpression of Ca channel β subunits was found to differentially influence nickel effects on α1A, as coexpression with β2a or with β4 resulted in larger current-voltage shifts than those observed in the presence of β1b, while elimination of the β subunit almost completely abolished the gating shifts. In contrast, block was similar for the
three β subunits tested, while complete removal of the β subunit resulted in an increase in blocking affinity. Our data suggest
that the effect of nickel on calcium channels is complex, cannot be described by a single site of action, and differs qualitatively
and quantitatively among individual subtypes and subunit combinations.
Received: 12 October 1995/Revised: 17 January 1996 相似文献
7.
The α1 subunit coding for the human brain type E calcium channel (Schneider et al., 1994) was expressed in Xenopus oocytes in the absence, and in combination with auxiliary α2δ and β subunits. α1E channels directed with the expression of Ba2+ whole-cell currents that completely inactivated after a 2-sec membrane pulse. Coexpression of α1E with α2bδ shifted the peak current by +10 mV but had no significant effect on whole-cell current inactivation. Coexpression of α1E with β2a shifted the peak current relationship by −10 mV, and strongly reduced Ba2+ current inactivation. This slower rate of inactivation explains that a sizable fraction (40 ± 10%, n= 8) of the Ba2+ current failed to inactivate completely after a 5-sec prepulse. Coinjection with both the cardiac/brain β2a and the neuronal α2bδ subunits increased by ≈10-fold whole-cell Ba2+ currents although coinjection with either β2a or α2bδ alone failed to significantly increase α1E peak currents. Coexpression with β2a and α2bδ yielded Ba2+ currents with inactivation kinetics similar to the β2a induced currents, indicating that the neuronal α2bδ subunit has little effect on α1E inactivation kinetics. The subunit specificity of the changes in current properties were analyzed for all four β subunit
genes. The slower inactivation was unique to α1E/β2a currents. Coexpression with β1a, β1b, β3, and β4, yielded faster-inactivating Ba2+ currents than currents recorded from the α1E subunit alone. Furthermore, α1E/α2bδ/β1a; α1E/α2bδ/β1b; α1E/α2bδ/β3; α1E/α2bδ/β4 channels elicited whole-cell currents with steady-state inactivation curves shifted in the hyperpolarized direction. The
β subunit-induced changes in the properties of α1E channel were comparable to modulation effects reported for α1C and α1A channels with β3≈β1b > β1a≈β4≫β2a inducing fastest to slowest rate of whole-cell inactivation.
Received: 27 March 1997/Revised: 10 July 1997 相似文献
8.
Alyson J. Laframboise Barbara S. Zielinski 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》2011,197(10):999-1008
The wild perciform teleost Neogobius melanostomus (the round goby) originated from the Ponto-Caspian region and is now a highly successful invasive species in the Laurentian
Great Lakes. Males may attract females into their nests for spawning by releasing reproductive pheromones, and it has been
previously shown that reproductive males synthesize and release the 5β-reduced and 3α-hydroxyl steroids 3α-hydroxy-5β-androstane-11,17-dione
(11-oxo-etiocholanolone; 11-O-ETIO) and 3α-hydroxy-5β-androstane-11,17-dione 3-sulfate (11-oxo-etiocholanolone-3-sulfate;
11-O-ETIO-3-s) and 3α,17β-dihydroxy-5β-androstan-11-one 17-sulfate. In this study, we investigated properties of these released
steroids by recording field potential responses from the olfactory epithelium (electro-olfactogram, EOG). The steroid 3α,17β-dihydroxy-5β-androstan-11-one
17-sulfate did not elicit olfactory responses while both 11-O-ETIO and 11-O-ETIO-3-s stimulated olfactory field potentials
in the round goby, but not in the goldfish. Cross-adaptation analysis demonstrated that round gobies discriminated between11-O-ETIO
and 11-O-ETIO-3-s (as well as etiocholanolone, ETIO) at the sensory level. Second messenger cascades depending on both cAMP
and IP3 were inferred for steroids from pharmacological inhibition studies, while the canonical teleost odors taurocholic acid (a
bile acid) and l-alanine (an amino acid) used only cAMP and IP3, respectively. The round goby presents itself as an excellent species for the study of olfactory function of fish in the
wild, given its possible use of these released steroids as pheromones. 相似文献
9.
T. V. Malyarenko A. A. Kicha N. V. Ivanchina A. I. Kalinovsky P. S. Dmitrenok A. V. Smirnov 《Russian Journal of Bioorganic Chemistry》2010,36(6):755-761
Thirteen steroidal compounds including three new polyhydroxysteroids, (24R,25S)-24-methyl-5α-cholestane-3β,6α,8,15β,16β,26-hexaol, (22E,24R,25S)-24-methyl-5α-cholest-22-ene-3β,6α,8,15β,16β,26-hexaol, and (22E,24R,25S)-24-methyl-5α-cholest-22-ene-3β,4β,6α,8,15β,16β,26-heptaol, have been isolated along with ten previously known polyhydroxysteroids
from the tropical starfish Asteropsis carinifera collected near the coast of Vietnam. The structures of the new compounds were elucidated by spectroscopic methods (mainly
2D NMR and ESI mass spectrometry). 相似文献
10.
YOSHITAKA NAGAHAMA FREDERICK W. GOETZ JOSEFA D. TAN 《Development, growth & differentiation》1986,28(6):555-561
Both partially purified chum salmon gonadotropin and 17α-hydroxyprogesterone stimulated in vitro production of testosterone by postvitellogenic follicles of goldfish ( Carassius auratus ). Chum salmon gonadotropin further enhanced the conversion of exogenously supplied 17α-hydroxyprogesterone to 17α, 20β-dihydroxy-4-pregnen-3-one. The increased medium concentrations of 17α, 20β-dihydroxy-4-pregnen-3-one were associated with the induction of final oocyte maturation.
The capacity of postvitellogenic follicles to produce steroids in response to exogenous 17α-hydroxyprogesterone was examined in females at various stages of final oocyte maturation following the administration of human chorionic gonadotropin in vivo combined with elevation of holding temperature. The maximum production of testosterone in response to 17α-hydroxyprogesterone was obtained in follicles from initial controls. In contrast, 17α 20β-diOHprog production was very low in initial controls and markedly increased during oocyte maturation (3–6 hr following injection), followed by a significant decrease in follicles collected at 15 hr. Estradiol-17β production by the follicles was very low at any stages of gonadotropin-induced oocyte maturation. These results suggest that gonadotropin-induced shift in the biosynthetic pathway in the follicle from the secretion of predominantly testosterone to 17α, 20β-dihydroxy-4-pregnen-3-one secretion is a prerequisite step for the induction of oocyte maturation in goldfish. 相似文献
The capacity of postvitellogenic follicles to produce steroids in response to exogenous 17α-hydroxyprogesterone was examined in females at various stages of final oocyte maturation following the administration of human chorionic gonadotropin in vivo combined with elevation of holding temperature. The maximum production of testosterone in response to 17α-hydroxyprogesterone was obtained in follicles from initial controls. In contrast, 17α 20β-diOHprog production was very low in initial controls and markedly increased during oocyte maturation (3–6 hr following injection), followed by a significant decrease in follicles collected at 15 hr. Estradiol-17β production by the follicles was very low at any stages of gonadotropin-induced oocyte maturation. These results suggest that gonadotropin-induced shift in the biosynthetic pathway in the follicle from the secretion of predominantly testosterone to 17α, 20β-dihydroxy-4-pregnen-3-one secretion is a prerequisite step for the induction of oocyte maturation in goldfish. 相似文献
11.
12.
To clarify the annual reproductive cycle of wild female mosquitofish,Gambusia affinis, in Mie Prefecture, central Japan, changes in ovarian histology were investigated. Female mosquitofish kept in aquaria under
constant temperature (25°C) and photoperiod (16L: 8D) conditions produced successive broods at intervals of 22.1±0.46 days
(n=7). Between days 0–3 following parturition, females began active vitellogenesis. Between days 3–5, fully grown oocytes matured
and were fertilized, and embryonic development began in the follicles. By day 10, as fertilized eggs continued embryonic development,
some oocytes at the oil-droplet stage had begun to accumulate yolk globules for the next gestation. Thus, vitellogenesis of
the succeeding batch of oocytes overlaps with gestation during reproduction in the mosquitofish. A rearing experiment showed
the annual reproductive cycle of mosquitofish breeding in Nagashima to be as follows. Although oocytes had not at that point
developed to the yolk globule stage, copulation occurred in February. Females began vitellogenesis in early May, the first
pregnancy of the year commencing in mid-May. From mid-May to August, females repeated the gestation cycle (vitellogenesis,
maturation, fertilization, pregnancy and parturition) at around one month intervals. In September, oocyte recruitment from
the oil-droplet to the yolk globule stage ceased. After the final parturition, the ovaries contained only non-vitellogenic
oocytes. Spermatozoa in the ovarian cavity were scare from November to January. 相似文献
13.
Rapid light-response curves (RLC) of variable chlorophyll fluorescence were measured on estuarine benthic microalgae with
the purpose of characterising its response to changes in ambient light, and of investigating the relationship to steady-state
light-response curves (LC). The response of RLCs to changes in ambient light (E, defined as the irradiance level to which a sample is acclimated to prior to the start of the RLC) was characterised by constructing
light-response curves for the RLC parameters α
RLC, the initial slope, ETRm,RLC, the maximum relative electron transport rate, and E
k,RLC, the light-saturation parameter. Measurements were carried out on diatom-dominated suspensions of benthic microalgae and
RLC and LC parameters were compared for a wide range of ambient light conditions, time of day, season and sample taxonomic
composition. The photoresponse of RLC parameters was typically bi-phasic, consisting of an initial increase of all parameters
under low ambient light (E < 21–181 μmol m−2 s−1), and of a phase during which α
RLC decreased significantly with E, and the increase of ETRm,RLC and E
k,RLC was attenuated. The relationship between RLC and LC parameters was dependent on ambient irradiance, with significant correlations
being found between α
RLC and α, and between ETRm,RLC and ETRm, for samples acclimated to low and to high ambient irradiances, respectively. The decline of α
RLC under high light (Δα
RLC) was strongly correlated (P < 0.001 in all cases) with the level of non-photochemical quenching (NPQ) measured before each RLC. These results indicate
the possibility of using RLCs to characterise the steady-state photoacclimation status of a sample, by estimating the LC parameter
E
k, and to trace short-term changes in NPQ levels without dark incubation. 相似文献
14.
By the use of the Immobiline technique at pH ranges 7.0–7.6 and 6.9–7.9, 16 different hemoglobin (Hb) phenotypes were observed
in 61 English Saanen goats. They are explained in this breed by a genetic theory of five β-globin genes (A
4,A
6,A
8,E, andD) and two closely linked α-globin loci (′α and ″α) of which the ″α has a variant allele, provisionally called ″α
X
. Family data together with observed and expected Hb frequencies were in agreement with the genetic theory. Among six Barbary
sheep there were three Hb phenotypes explained by the occurrence of the β-chain allelesB andC
na. 相似文献
15.
H. J. Carlisle T. G. Hales B. A. Schlinger 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1998,182(4):531-538
Songbirds are widely studied to investigate the hormonal control of behavior. However, little is known about the effects
of steroids on neurotransmission in these birds. We used electrophysiological and pharmacological techniques to characterize
γ-aminobutyric acid (GABA) type A receptors (GABAA) of primary cultured telencephalic and hippocampal neurons from developing zebra finches. Additionally, their modulation
by 17β-estradiol(E2), 5α- and 5β-dihydrotestosterone (DHT), 5α- and 5β-pregnan-3α-ol-20-one, and corticosterone was examined. Whole-cell GABA-evoked
currents were inhibited by picrotoxin (10 μmol l−1) and bicuculline methiodide (10 μmol l−1) and potentiated by pentobarbital (100 μmol l−1) and propofol (3 μmol l−1). Loreclezole (10 μmol l−1) potentiated GABA-evoked currents, suggesting the presence of β2, β3 and/or β4 subunits. Diazepam (1 μmol l−1) potentiated currents, while Zn2+ (1 μmol l−1) caused no inhibition, indicating the presence of γ subunits. 5α- and 5β-Pregnan-3α-ol-20-one (100 nmol l−1) potentiated currents, whereas E2 (1 μmol l−1), 5α- and 5β-DHT (1 μmol l−1), and corticosterone (10 μmol l−1) had no detectable effect. We conclude that zebra finch telencephalic and hippocampal GABAA receptors include α, β, and γ subunits and are similar to their mammalian counterparts in both their biophysical and pharmacological
properties. Additionally, GABA-evoked currents are greatly potentiated by 5α- and 5β-pregnan-3α-ol-20-one but show little
or no acute modulation by sex steroids or corticosterone.
Accepted: 12 November 1997 相似文献
16.
17.
GABAA receptors composed of α, β and γ subunits display a significantly higher single-channel conductance than receptors comprised
of only α and β subunits. The pore of GABAA receptors is lined by the second transmembrane region from each of its five subunits and includes conserved threonines at
the 6′, 10′ and 13′ positions. At the 2′ position, however, a polar residue is present in the γ subunit but not the α or β
subunits. As residues at the 2′, 6′ and 10′ positions are exposed in the open channel and as such polar channel-lining residues
may interact with permeant ions by substituting for water interactions, we compared both the single-channel conductance and
the kinetic properties of wild-type α1β1 and α1β1γ2S receptors with two mutant receptors, αβγ(S2′A) and αβγ(S2′V). We found
that the single-channel conductance of both mutant αβγ receptors was significantly decreased with respect to wild-type αβγ,
with the presence of the larger valine side chain having the greatest effect. However, the conductance of the mutant αβγ receptors
remained larger than wild-type αβ channels. This reduction in the conductance of mutant αβγ receptors was observed at depolarized
potentials only (ECl = −1.8 mV), which revealed an asymmetry in the ion conduction pathway mediated by the γ2′ residue. The substitutions at the
γ2′ serine residue also altered the gating properties of the channel in addition to the effects on the conductance with the
open probability of the mutant channels being decreased while the mean open time increased. The data presented in this study
show that residues at the 2′ position in M2 of the γ subunit affects both single-channel conductance and receptor kinetics. 相似文献
18.
Kim Y Lucas CA Zhong WW Hoh JF 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2007,177(6):701-705
Ventricular myosin in eutherian mammals undergoes a perinatal change in response to a sharp rise in thyroid hormone levels
during development. In this investigation, changes in ventricular myosin heavy chains (MyHCs) of the tammar wallaby (Macropus eugenii) from early pouch life to adulthood were analysed using native gel electrophoresis, SDS-PAGE and western blotting. Adult
wallaby ventricle showed three myosin isoenzymes, V1, V2 and V3; western blots using specific anti-α-MyHC and anti-β-MyHC antibodies showed their MyHC compositions to be αα, αβ and ββ,
respectively. Ventricular muscle in early pouch joeys expressed predominantly β-MyHC. Up to 200 days, the time of initial
pouch exit, α-MyHC content was around 5%. Thereafter, there was a sharp increase of α-MyHC expression to 35% by 242 days of
age, eventually falling back to 23% in the adult. These changes correlate with known surges in plasma levels of thyroid hormones
around pouch exit. The results suggest that ventricular myosins in a marsupial mammal also undergo a developmental change,
and that marsupial ventricular myosins are thyroid responsive as in eutherians. The increased α-MyHC expression empowers the
heart to meet the enhanced cardiovascular demands of out-of-pouch activity and the thermogenic action of thyroid hormones. 相似文献
19.
L. F. Canosa A. G. Pozzi N. R. Ceballos 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1998,168(7):491-496
Sliced testis tissue from Bufo arenarum was incubated in the presence of [3H]pregnenolone. Testis fragments were also used for double isotope experiments using [3H]pregnenolone and [14C]progesterone. Specific activities were equated with the addition of radioinert pregnenolone. When yields of radiometabolites
were analysed, pregnenolone was found to be a good precursor for C19 steroids such as dehydroepiandrosterone, 5-androsten-3β,17β diol, testosterone, 5α-dihydrotestosterone and a C21 steroid, 5α-pregnan-3,20 dione. Progesterone mainly converts to 5α-pregnan-3,20 dione, a steroid with unknown function in
amphibians. The 5-ene pathway, including 5-androsten-3β,17β diol as intermediate, could be predominant for androgen biosynthesis.
Testes bypass not only progesterone but also androstenedione for testosterone biosynthesis.
Accepted: 17 April 1998 相似文献
20.
Steroid hormones, beside their classical genomic mechanism of action, exert rapid, non genomic effects in different cell types.
These effects are mediated by still poorly characterized plasma membrane receptors that appear to be distinct from the classic
intracellular receptors. In the present study we evaluated the non genomic effects of estradiol (17βE2) in human sperm and its effects on sperm stimulation by extracellular ATP, a potent activator of sperm acrosome reaction.
In human sperm 17βE2 induced a rapid increase of intracellular calcium (Ca2+) concentrations dependent on an influx of Ca2+ from the extracellular medium. The monitoring of the plasma membrane potential variations induced by 17βE2 showed that this steroid induces a rapid plasma membrane hyperpolarization that was dependent on the presence of Ca2+ in the extracellular medium since it was absent in Ca2+ free-medium. When sperm were pre-incubated in the presence of the K+ channel inhibitor tetra-ethylammonium, the 17βE2 induced plasma membrane hyperpolarization was blunted suggesting the involvement of K+ channels in the hyperpolarizing effects of 17βE2. Extracellular ATP induced a rapid plasma membrane depolarization followed by acrosome reaction. Sperm pre-incubation with
17βE2 inhibited the effects of extracellular ATP on sperm plasma membrane potential variations and acrosome reaction. The effects
of 17βE2 were specific since its inactive steroisomer 17αE2 was inactive. Furthermore the effects of 17βE2 were not inhibited by tamoxifen, an antagonist of the classic 17βE2 intracellular receptor. 相似文献