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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The objective of this study was to determine the requirements for the functional luteinization of porcine thecal cells in vitro. In serum-free incubations with luteinizing hormone (LH) (250 ng/ml) androstenedione concentrations increased up to 14 h, after which time no further accumulation occurred; progesterone accumulation was low, and did not increase after 4 h. In the presence of 1% fetal bovine serum and LH, androstenedione production declined, but progesterone production per day increased over a 4-day period, while cellular protein remained constant. LH was required for both the induction and maintenance of elevated progesterone production. Insulin (maximal response at 500 ng/ml) in the presence of 1% serum enhanced the response to LH, causing a dramatic increase in progesterone production, an effect which became greater with time in culture. Dose-response curves for insulin and insulin-like growth factor I (IGF-I) were parallel, but IGF-I was approximately 23-fold more potent than insulin, suggesting that insulin was acting through IGF-I receptors. Our results show that porcine thecal cells, in the presence of LH, insulin or IGF-I, and 1% serum, undergo functional luteinization in vitro, such that androstenedione production declines, and the rate of progesterone production increases with time in culture.
Mol Cell Endocrinol 1991 Mar
PMID:Luteinization of porcine thecal cells in vitro. 202 77

The objective of the present study was to develop a chemically-defined medium in which early stages of testicular differentiation can be investigated in an organ culture system. Mouse gonadal primordia were explanted before and after initiation of morphological sex differentiation, i.e. 11 and 12 day of gestation (d.g.), respectively. We found that a combination of human albumin fraction, insulin (or IGF-I), and sodium pyruvate promoted testicular organization of gonadal explants of 11 d.g., but not those of 12 d.g. Insulin also increased the production of testosterone from testicular explants of 11 d.g., but not those of 12 d.g. For the younger explants, progesterone was more efficient than pregnenolone as a steroid precursor during the first day of culture, but the maximum effect of pregnenolone was much higher than that of progesterone in later stages. The responsiveness to human chorionic gonadotropin increased gradually along with testicular organization. The addition of either serum or pregnenolone prominently increased the activity of delta 5-3 beta hydroxysteroid dehydrogenase in testicular explants of 11 d.g., but not the number of positive cells as demonstrated by histochemical staining. These results suggest that insulin (or IGF-I) is required during the initial phase of testicular organization, which is reflected by an increase in testosterone production and sensitivity to gonadotropins.
J Steroid Biochem Mol Biol 1991 Apr
PMID:Regulation of testicular differentiation and testosterone production in the fetal mouse gonad in vitro. 203 66

The effect of several methylputrescines on the activity of insulin-induced ornithine decarboxylase (ODC) was examined in H-35 hepatoma cells. The induction involved both protein and m-RNA synthesis. Actinomycin D inhibited ODC activity when given up to 1 h after insulin treatment. When added to the medium 2 h or 3 h after the insulin, the activity was increased 100% and 80% respectively. Insulin-induced ODC from H-35 cells had a biphasic half-life, a shorter one of 46 min and a longer one of 90 min. 1-Methylputrescine and 2-methylputrescine were found to be competitive inhibitors of the ODC from H-35 cells with Ki values of 2.8 and 0.1 mM respectively. Putrescine itself was found to have a Ki = 2.4 mM. N-Methylputrescine was a very poor inhibitor of the cell free ODC while 1,4-dimethylputrescine did not show any inhibitory effect. When cellular ODC activity was measured, the four methylputrescines assayed as well as putrescine entirely abolished its activity in the H-35 cells when given at a 1 mM concentration together with insulin. 1-Methylputrescine and 1,4-dimethylputrescine abolished 60% of the activity at a 0.1 microM concentration. All the methylputrescines given at 0.1 mM concentrations decreased the putrescine content of the stimulated cells to the levels found in quiescent cells, but only 1-methyl and 2-methylputrescines decreased spermidine and spermine content. 1,4-Dimethyl and 1-methylputrescines showed a strong inhibition of ODC synthesis, while the other diamines were less inhibitory. At concentrations that abolished ODC activity, 1,4-dimethylputrescine decreased 70% of the total immunoreactive ODC bands, while 1-methyl and 2-methylputrescine decreased them by 50%, and N-methylputrescine and putrescine decreased them by 20%. The lack of decrease in immuno-reactive ODC with the latter two compounds was mainly due to the appearance of immunoreactive degradation products of ODC of low molecular weight. Putrescine and N-methylputrescine affected protein synthesis to a small extent in stimulated cells, while 1-methylputrescine decreased it to the level of non-stimulated cells. Insulin (1 microM concentration) stimulated DNA synthesis in the cells, and this stimulation was doubled in the presence of 2-methylputrescine or putrescine. It can be concluded that, among the methylputrescines assayed, 2-methylputrescine was the best inhibitor of cell-free ODC activity, while 1,4-dimethylputrescine and 1-methylputrescine were the best inhibitors of cellular ODC activity.
Mol Cell Biochem 1991 Jan 16
PMID:Modulation of insulin induced ornithine decarboxylase by putrescine and methylputrescines in H-35 hepatoma cells. 205 98

The production of insulin-like growth factor I (IGF-I) by pig Leydig cells and pig Sertoli cells cultured alone or together was investigated. Human chorionic gonadotropin (hCG) and basic fibroblast growth factor (FGF) stimulate in a dose-dependent manner IGF-I production by Leydig cells. At maximal concentrations the effects of both factors were almost additive. Insulin at micromolar concentrations enhanced IGF-I production and potentiated the effects of hCG and FGF. The secretion of IGF-I by Sertoli cells was stimulated by FSH and FGF. Under basal conditions, the production of IGF-I by the coculture was similar to the addition of the production by each cell cultured alone. In contrast, in the presence of hCG, FSH or FGF, the production of IGF-I by the coculture largely exceeded that expected from the monocultures. Moreover, stimulation of the coculture with both hCG and FSH resulted in a further increase in IGF-I production. These results indicate that Leydig as well as Sertoli cells secrete IGF-I and that the secretion of both cell types is stimulated by the corresponding gonadotropin. In addition, they indicate that Leydig-Sertoli interactions play a role in the control of IGF-I production, supporting the contention that this growth factor plays an important role in the paracrine and autocrine control of testicular functions.
Mol Cell Endocrinol 1990 May 07
PMID:Control of production of insulin-like growth factor I by pig Leydig and Sertoli cells cultured alone or together. Cell-cell interactions. 211 75

Primary culture of guinea-pig endometrial cells was made quiescent by serum depletion. When added to quiescent cells, 17 beta-estradiol (E2) alone affected neither c-fos and c-myc gene expression, nor DNA synthesis and cell proliferation. Insulin or epidermal growth factor (EGF) only induced DNA synthesis. An association of both growth factors allowed significant cell proliferation without inducing c-fos or c-myc expression. A response including c-fos induction (maximal expression at 75 min), but not c-myc expression, DNA synthesis and a marked cell proliferation was only obtained when 17 beta-estradiol was associated with insulin plus EGF. In this case, cycloheximide raised the c-fos gene expression. These data suggest that in endometrial epithelial cells, E2 is mitogenic only when it acts in association with EGF plus insulin and the c-fos gene expression may not be correlated with cell proliferation.
Mol Cell Endocrinol 1990 Sep 10
PMID:Effects of 17 beta-estradiol and growth factors on c-fos gene expression in endometrial epithelial cells in primary culture. 212 27

Insulin resistance caused by dexamethasone administration to rats was accompanied by a marked decrease in the hepatocyte content of an insulin-sensitive glycosyl-phosphatidylinositol, as well as by a blockade of its hydrolysis in response to this hormone. In contrast, bilateral adrenalectomy provoked a significant increase of the cellular glycosyl-phosphatidylinositol levels. Under all the assayed metabolic conditions, a close direct correlation was established between the basal content of this compound and the number of insulin receptors present in the isolated hepatocytes.
Mol Cell Endocrinol 1990 Jan 02
PMID:Effect of adrenalectomy and glucocorticoid treatment on the levels of an insulin-sensitive glycosyl-phosphatidylinositol in isolated rat hepatocytes. 213 22

The enhanced phosphorylations via cAMP, Ca2+ mobilization, and diacyl glycerol formation via the activation of the respective kinases is now classical. The decreased phosphorylation via inhibition of adenylate cyclase via the alpha adrenergic receptor is also becoming understood. What the insulin studies on the control of glycogen synthesis have taught us is that the rate limiting enzyme glycogen synthase is regulated by multiple covalent phosphorylation in an elegant but complex manner. The overall pattern of dephosphorylation is influenced by effecting both phosphatase and kinase activities in a set of interrelated mechanisms. In the presence of glucose, in muscle, fat, and liver under physiological conditions G-6-P acts as a signal to stimulate the phosphatase. An additional stimulation could occur via a novel insulin phosphatase stimulatory mediator. The phosphatase is also stimulated by at least three covalent mechanisms involving altered phosphorylation state. In one there is a decreased phosphorylation of the phosphatase inhibitor 1 potentially related to decreased cAMP-dependent protein kinase activity. In the second, there is decreased phosphorylation of the deinhibitor also potentially related to decreased cAMP-dependent protein kinase phosphorylation. In the third, an increased activity of casein kinase 2 could activate the ATP-Mg dependent phosphatase by an increased phosphorylation of phosphatase inhibitor 2 (modulatory subunit). In the liver, allosteric control of the phosphatase by G-6-P and nucleotides is of great importance. Insulin also stimulates the phosphatase in long-term experiments via increased protein synthesis. It is clear that future work will be required to determine which species of the various classes of phosphatases are regulated in short-term and long-term regulation by insulin. In terms of kinases, the effects of insulin to inactivate and desensitize the cAMP-dependent protein kinase are established. The molecular mechanisms of this effect remain to be worked out. The enhanced activity of MAP and S-6 kinase would appear to be part of a cascade of reactions perhaps originating in the autophosphorylation and activation of the insulin receptor tyrosine kinase. The mechanism of the short-term activation of casein kinase 2 remains to be elucidated. A cAMP-dependent protein kinase inhibitory mediator, which also inhibits adenylate cyclase is an important element in the regulation of kinase and adenylate cyclase activity by insulin. Its physiological significance must be established in the future, in terms of its control of glycogen synthase activation by insulin. Clearly this kinase inhibitor as well as the phosphatase stimulator are potential regulators of glycogen synthase activity by insulin.
Adv Enzymol Relat Areas Mol Biol 1990
PMID:Insulin and the stimulation of glycogen synthesis. The road from glycogen structure to glycogen synthase to cyclic AMP-dependent protein kinase to insulin mediators. 215 10

The action of insulin and sodium vanadate on the phosphorylation of uridine by skeletal muscle was studied in vitro. Insulin significantly increased the incorporation of 3H-uridine into uracil nucleotides by pieces of rat diaphragm incubated for 15 min in a phosphate-buffered medium. This action of the hormone was exceptionally consistent when MgATP was added to the incubation medium. In experiments in which pieces of psoas muscle were incubated in TRIS buffer in the presence and absence of insulin, the hormone caused a significant activation of uridine kinase measured in cytosolic extracts of the incubated tissue. In experiments with rat diaphragm similar to those with insulin, the vanadate ion caused a significant increase in phosphorylation of uridine. The results of these experiments provide preliminary support for the proposal that uracil nucleotide metabolism is regulated by insulin and that insulin activates uridine kinase, the limiting enzyme in the synthesis of uracil nucleotides from uridine by the salvage pathway.
Mol Cell Biochem 1990 Mar 05
PMID:Stimulation of the phosphorylation of uridine in skeletal muscle by insulin and vanadate. 215 18

Stimulation of ornithine decarboxylase (ODC) activity was examined in cultured heart cells from neonatal rats. Fetal bovine serum had a concentration-dependent effect on ODC activity with maximum response obtained at 10% serum. ODC activity peaked 4 h after the addition of serum and returned to initial levels at 8 h. In the absence of serum, non-cytotoxic concentrations of the adrenergic agonists epinephrine, norepinephrine or isoproterenol did not stimulate ODC activity. Co-administration of serum and catecholamines at 10(-5) M induced an ODC response that was significantly greater than that induced by serum alone. A screen of various constituents of serum revealed that insulin, though relatively ineffective alone, acted cooperatively with catecholamines to produce an ODC response equivalent to that induced by 10% serum. Propranolol effectively blocked the cooperative effect of insulin on catecholamine stimulation of ODC activity, and markedly inhibited the stimulation of ODC by 10% serum. Insulin also acted cooperatively with the second-messenger analogue dibutyryl-cAMP. The calcium ionophore A23187 significantly increased ODC activity and this response was potentiated by the presence of insulin. The present findings are concordant with in vivo observations in that beta-adrenergic activation stimulates ODC activity in cultured heart cells, but it also demonstrates that the cooperative action of other factors present in serum, such as insulin, are required.
J Mol Cell Cardiol 1990 Jun
PMID:Cooperative action of insulin and catecholamines on stimulation of ornithine decarboxylase activity in neonatal rat heart cells. 217 54

The present studies examined responses to hCG and/or insulin of 3 beta-hydroxy-5-ene-steroid dehydrogenase and steroid 5----4-ene-isomerase activity (3 beta-HSD) in cultured Band 2 and Band 3 cells from 25- to 40-day-old rats isolated on Percoll gradients. In Band 2 cells, from 25-day-old rats enzyme activity increased about 3- and 2.5-fold, after 6 days of exposure to hCG or insulin, respectively. However, hCG did not stimulate enzyme activity in Band 2 cells from 30-, 35- and 40-day-old animals, and responses to insulin alone or insulin plus hCG declined with age. In Band 3 cells only insulin increased enzyme activity at each age. Neither hCG or insulin altered DNA levels in Band 2 or Band 3 cells, suggesting that increased activity in Band 2 cells from 25-day-old rats was not due to cellular replication. However, hCG increased the number of cells staining positive for 3 beta-HSD about 4-fold in Band 2 cells from 25-day-old rats. Insulin did not increase the number of positive staining cells in Band 2 and Band 3 cells from 25-day-old rats, suggesting that its major effect was to increase enzyme activity in existing cells. These results suggest that during a limited period of maturation precursor cells in Band 2, which are undetected by histochemical staining for 3 beta-HSD, can be converted to Leydig cells in culture by hCG.
J Steroid Biochem Mol Biol 1990 Dec 10
PMID:Evidence that Leydig precursors localize in immature band two cells isolated on Percoll gradients. 217 28


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