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11.
In previous studies cadmium chloride (CdCl2) nonlethally inhibited Y-1 adrenal mouse adrenal tumour cell 20-dihydroxyprogesterone (20DHP) secretion, affecting unstimulated and stimulated steroidogenic pathway sites differently. We studied CdCl2 effects on unstimulated steroidogenesis using Y-1 cells incubated 0.5 h in medium with or without cadmium (using the concentration that inhibited ACTH-stimulated steroid secretion by 50%). Exogenously added 20-hydroxycholesterol (20OHC), 22(R)-hydroxycholesterol (22OHC), 25-hydroxycholesterol (25OHC), pregnenolone (PREG), or progesterone (PROG) were used to bypass any rate-limited steroidogenic pathway sites that CdCl2 might inhibit. 25OHC is a biologically active nonpathway steroid, while 20OHC, 22OHC, PREG, and PROG are pathway steroids; each increased unstimulated 20DHP secretion nearly 10-fold. Although CdCl2 could not reduce dibutyryl cyclic AMP- (dbcAMP)-stimulated 20DHP secretion significantly, it did significantly reduce basal and 25OHC-induced 20DHP secretion 25% below untreated levels. When 20OHC, 22OHC, PREG, or PROG were incubated with unstimulated Y-1 cells, their synthesis into 20DHP was unaffected by cadmium. dbcAMP bypasses the plasma membrane enzyme complex that synthesizes intracellular cAMP during exogenous ACTH stimulation; dbcAMP was not inhibited by CdCl2. The rate-limited step accelerated by cAMP involves plasma membrane and/or cytoplasmic cholesterol transport to and through outer and inner mitochondrial membranes before the cholesterol is synthesized into pregnenolone by side-chain cleavage enzymes on the inner membrane matrix face. Little is known regarding the mechanisms controlling unstimulated steroidogenesis. Under unstimulated conditions the 25-, 20- and 22(R)-monohydroxyls of cholesterol facilitate plasma membrane, cytoplasm and inner and outer mitochondrial solubility, diffusion and/or transport to bypass rate-limited steps and augment unstimulated steroid synthesis. Since conversion of endogenous mitochondrial cholesterol and 25OHC, but not dbcAMP-mobilized cytoplasmic cholesterol, 20OHC or 22OHC conversion, to 20DHP is inhibited by CdCl2, this suggests that (a) control of mitochondrial cholesterol supplies is independent of the cAMP-regulated mitochondrial steps in the 20DHP steroid synthetic pathway, (b) CdCl2 specifically inhibited endogenous mitochondrial cholesterol and 25OHC utilization, (c) CdCl2 toxicity may affect adrenal, testicular, ovarian, and placental basal steroidogenic functions, and (d) 25OHC may be a useful compound to examine unstimulated steroid synthesisAbbreviations ACTH
adrenocorticotropin
- ANOVA
analysis of variance
- CdCl2
cadmium chloride
- cAMP
cyclic 3,5-adenosine monophosphate
- DMSO
dimethylsulfoxide
- DNA
deoxyribonucleic acid
- FMEM
serum-free Eagle's Minimum Essential Medium
- Hepes
N-2-hydroxyethyl-piperazine-N-1,2-ethanesulfonic acid
- 20OHC
20-hydroxycholesterol
- 22OHC
22(R)-hydroxycholesterol
- 25OHC
25-hydroxycholesterol
- IC50'
concentration inhibiting stimulated steroid secretion by 50%
- IU
international unit
- MEM
Eagle's Minimum Essential Medium
- P450scc
cytochrome P450 side-chain cleavage enzyme
- PREG
pregnenolone
- PROG
progesterone
- RNA
ribonucleic acid
- SEM
standard error of the mean
- SMEM
serum-containing Eagle's Minimum Essential Medium
- 20DHP
20-hydroxy-4-pregnen-3-one 相似文献
12.
13.
Iain F.H. Purchase Christopher R. Richardson Diana Anderson Geoffrey M. Paddle William G.F. Adams 《Mutation research》1978,57(2):325-334
Chromosomal morphology from cultured peripheral lymphocytes was studied in 81 men; 57 of the men were employed on plants manufacturing vinyl chloride or polyvinylchloride, 19 were on-site controls and 5 were off-site controls. There was a significant increase in chromosomal abnormalities in the exposed workers when compared with the controls. The greatest statistically significant increase in total B and total C cells occurred in autoclave operators, with smaller increases in other job categories. The increase in chromosomal aberrations was correlated with the length of exposure and with a history during the year prior to sampling (1973–1974) of exposure to excursion levels of vinyl chloride. Information on smoking habits was obtained 18 months after blood sampling and a positive correlation between these and total C cell abnormalities was found. There was no positive correlation with various other parameters (bilirubin, platelets, γ-glutamyltranspeptidase, alkaline phosphatase, alanine transaminase and aspartate transaminase). It was not possible to estimate which of the three parameters (smoking history, length of employment or exposure to excursion levels) was the most important. 相似文献
14.
John C. Angello Howard L. Hosick 《Biochemical and biophysical research communications》1982,107(3):1130-1137
Multicellular aggregates of tumorigenic mouse mammary epithelial cells contain a hyaluronate-rich matrix, both at the aggregate periphery and within the growing spheroid. It is proposed that the establishment of a hyaluronaterich matrix is essential to spheroid growth in vitro, and that the spheroid is a good model system for analysis of this aspect of early tumor development. 相似文献
15.
Extracts of bovine aorta and nuchal ligament contain several large glycoproteins. The major glycoprotein species has been isolated and has been shown to be collagenase sensitive with an apparent molecular weight of 140,000 daltons. The protein exists in disulphide-bonded aggregates, contains hydroxyproline and hydroxylysine in 1:1 ratio and is unlike any of the known collagen types in amino acid analysis. Its presencein ligament extracts indicates that it is not derived from basement membranes. The evidence suggests that this protein is not derived from the microfibrillar components of the elastic tissues. 相似文献
16.
Mario Díaz Antonio Lorenzo 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1992,162(2):189-196
Summary Bioelectrical parameters and unidirectional sodium and chloride fluxes were measured under voltageclamp conditions in groups of lizards submitted to single or chronic aldosterone treatment. Both acute (AT) and chronic (CT) treatment induced significant increases in the short-circuit current (I
sc), as well as in the mucosa-to-serosa (J
m-s
Na
) and net sodium flux (J
net
Na
). In AT tissues, aldosterone did not change net chloride flux (J
net
Cl
) but did so in CT tissues. Amiloride reduced the aldosterone-increased I
sc in AT and CT tissues, inhibited J
net
Na
in AT tissues and abolished it in CT colons. J
net
Cl
was also reduced by the diuretic in the group of AT colons, whereas no changes were observed in the CT tissues. Addition of luminal DIDS reduced Na+ absorption and totally inhibited Cl- absorption in the AT tissues, but did not change I
sc. However, in CT tissues neither Na+ nor Cl- transport were affected by DIDS. A good relationship between I
sc and J
m-s
Na
was apparent after DIDS treatment in AT tissues. In this group, simultaneous addition of DIDS and amiloride totally abolished J
net
Na
and reduced I
sc to untreated control values. Addition of serosal ouabain abolished I
sc and Na+ absorption in AT and CT colons, but Cl- absorption was only altered in AT tissues. These results support the hypothesis that aldosterone induces an electrogenic, amiloride-sensitive sodium absorption, and in a dose-dependent fashion suppresses electroneutral NaCl absorption in the lizard colon.Abbreviations AT
acutely treated
- CT
chronically treated animals
- DIDS
4-4-diisothiocyanatostibene-2-2-disulfonic acid
- DMSO
dimethylsulphoxide
-
G
t
tissue conductance
-
I
sc
short circuit current
- PD
transepithelial potential difference
- SITS
4-acetamido-4-isothiocyanatostilbene-2-2-disulfonic acid
- UC
untreated controls
Preliminary results of this paper were presented at the X
th meeting of the European Intestinal Transport Group (EITG), Askov Hojskole, Denmark, 16–19 September 1990 相似文献
17.
Phosphorylation of troponin T by casein kinase TS 总被引:3,自引:0,他引:3
L A Pinna F Meggio M M Dediukina 《Biochemical and biophysical research communications》1981,100(1):449-454
18.
Summary Sodium and chloride influxes across the nonshort-circuited isolated skin ofRana esculenta were measured at widely varying external ionic concentrations.The curve describing sodium transport has two Michaelis-Menten components linked at an inflection point occurring at an external sodium concentration of about 7 meq. Chloride transport can also be represented by two saturating components. A possible explanation of these kinetics is discussed.At sodium concentrations lower than 4 meq it is possible to define a component of the sodium transport mechanism as having a high affinity for sodium and which is independent of the nature of the external anion. A high affinity for chloride of the chloride transport system functioning at low external concentrations is also found but is significantly different from that of sodium. These systems show the physiological characteristics of the countertransports (Na
ext
+
/H
int
+
; Cl
ext
–
/HCO
3int
–
) functioning at low external concentrations.At external concentrations higher than 4 meq a low affinity transporting system in which chloride and sodium are linked superimpose on the high affinity components.The physiological significance of these results is discussed. 相似文献
19.
Involvement of regulatory volume decrease in the migration of nasopharyngeal carcinoma cells 总被引:7,自引:0,他引:7
Mao JW Wang LW Jacob T Sun XR Li H Zhu LY Li P Zhong P Nie SH Chen LX 《Cell research》2005,15(5):371-378
The transwell chamber migration assay and CCD digital camera imaging techniques were used to investigate the relationship between regulatory volume decrease (RVD) and cell migration in nasopharyngeal carcinoma cells (CNE-2Z cells). Both migrated and non-migrated CNE-2Z cells, when swollen by 47% hypotonic solution, exhibited RVD which was inhibited by extracellular application of chloride channel blockers adenosine 5‘-triphosphate (ATP), 5-nitro-2-(3-phenylpropylamino) benzoic acid (NPPB) and tamoxifen. However, RVD rate in migrated CNE-2Z cells was bigger than that of non-migrated cells and the sensitivity of migrated cells to NPPB and tamoxifen was higher than that of nonmigrated cells. ATP, NPPB and tamoxifen also inhibited migration of CNE-2Z cells. The inhibition of migration was positively correlated to the blockage of RVD, with a correlation coefficient (r) = 0.99, suggesting a functional relationship between RVD and cell migration. We conclude that RVD is involved in cell migration and RVD may play an important role in migratory process in CNE-2Z cells. 相似文献
20.