Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P56851 (epididymal)
 11,273 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Isolated fat cells from rat epididymal adipose tissue were incubated with various lipolytic hormones in the absence and presence of the alpha-adrenergic blocking agent phentolamine. Lipolysis, stimulated by noradrenaline, isoproterenol, or ACTH, was inhibited dose-dependently by phentolamine. At concentrations of phentolamine where lipolysis was already inhibited, phentolamine had a biphasic effect on hormone-stimulated formation of cAMP. Low concentrations of phentolamine enhanced cAMP formation, while high concentrations inhibited cAMP. The additional increase of cAMP formation by phentolamine was only seen with maximally effective concentrations of noradrenaline, isoproterenol, and ACTH. Half-maximally effective concentrations were invariably inhibited by phentolamine. The activity of noradrenaline-stimulated adenylate cyclase of fat-cell plasma membranes was inhibited by phentolamine, whereas cAMP phosphodiesterase activity was unaffected.
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PMID:Biphasic effect of the alpha-adrenolytic phentolamine on hormone-stimulated formation of cyclic adenosine-3',5'-monophosphate in isolated fat cells of rats. 16 51

Preincubation of isolated epididymal fat cells with dexamethasone or treating rats with cortisol enhances the epinephrine-stimulated lipolysis of the cells as well as cAMP-dependent protein kinase activity in homogenates of these fat cell suspensions. During maximal inhibition of phosphodiesterase activity by theophylline or dibutyryl cAMP, this potentiating effect of glucocorticoids on the fat cells was also present. There was no lowering of the total phosphodiesterase activity in homogenates of fat cell suspensions of rats that were treated with cortisol, but there appeared to be a lower activity of the low KM phosphodiesterase activity. It is concluded that induction of protein kinase by glucocorticoid hormone is responsible for its special type of stimulative action on lipolysis.
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PMID:The mechanism of the potentiating effect of glucocorticoids on catecholamine-induced lipolysis. 16 65

There appear to be two classes of protein kinases in rat heart and adipose tissue, types I and II. Type I elutes from DEAE-cellulose at smaller than 0.1 M NaCl and type II at greater than 0.1 M NaCl. The type I enzyme is more readily dissociated by salt or histone than is the type II enzyme. If the type I kinase is first dissociated by cAMP, the subunits reassociate very slowly at 0 degrees C on removal of the cAMP by Sephadex G-25 chromatography, whereas those of type II reassociate very rapidly. Rat heart contains mostly type I and a small amount of type II enzyme, whereas adipose tissue contains almost exclusively the type II enzyme. The adipose tissue enzyme resembles the heart type II kinase in all of the above properties, although the two enzymes are not identical as indicated by slight differences in elution patterns from DEAE-cellulose columns. Incubation of rat epididymal adipose tissue with low concentrations of epinephrine (0.11 muM) increases glycerol production and the fraction of the protein kinase in the active form (activity ratio). The change in cAMP under these conditions is not statistically significant. The presence of insulin inhibits the epinephrine effect on glycerol production and protein kinase but has no measurable effect on cAMP levels. Incubation of adipose tissue with high epinephrine concentrations (11 muM) increases the cAMP level, the protein kinase activity ratio, and glycerol production. Under these conditions insulin decreases the cAMP level and kinase activity ratio but does not reduce glycerol production. The data suggest that very small changes in the tissue cAMP level, undetectable by the assay method, are magnified during the stepwise activation of glycerol output aided possibly by cooperative effects between cAMP and protein kinase. The procedure developed for determining the state of activation of the cAMP-dependent protein kinase in adipose tissue must be modified by reducing the salt concentration of the buffers in order to carry out similar studies in the heart. This reflects the different types of protein kinase in the two tissues. The addition of charcoal to crude extracts of heart prevents protein kinase activation by added cyclic AMP. Charcoal should therefore prevent any activation that could occur if any sequestered cAMP were released during homogenization. Charcoal addition thereby provides a means to distinguish intracellular cAMP activation of the kinase from that which might occur following cell rupture. If epinephrine-perfused hearts are homogenized in the presence of charcoal, epinephrine stimulation of the protein kinase is only slightly decreased. This indicates that the protein kinase is activated intracellularly by cAMP and suggests that all of the cAMP in the cell is available to the protein kinase; i.e., cAMP is not released during homogenization.
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PMID:Hormonal regulation of adenosine 3',5'-monophosphate-dependent protein kinase. 16 70

Rat epididymal tubules maintained in organ culture for 3 days respond to the addition of androgens to the culture media (testosterone and dihydrotestosterone 1 x 10-minus 5 m and 1 x 10-minus 7 m) with an increased incorporation of amino acids into acid-insoluble material. Significant androgenic stimulation is observed only 24 h after addition of hormone, while an inhibitory effect is found at earlier periods. The stimulation seems to be specifically produced by androgens; it is blocked by cyproterone acetate and is not elicited by oestradiol-17beta or corticosterone. The process appears to involve RNA synthesis since actinomycin D suppresses the stimulatory effect of androgen. Evidence suggests that cAMP production is not a primordial step in the response to androgen since dibutyryl cAMP did not mimick the androgenic effect, theophylline did not potentiate the response and alpha,beta-methylene ATP, which competitively inhibits adenyl cyclase, failed to alter the androgenic effect. Radioactive testosterone and dihydrotestosterone added to the culture media showed a preferential intranuclear localization as well as extensive metabolism. DHT was found to be the principal intranuclear steroid.
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PMID:The influence of androgens on protein synthesis by cultured rat epididymal tubules. 16 37

3':5'-Cyclic-AMP phosphodiesterase (PDE) (EC 3.1.4.17) activity was measured in interscapular brown adipose tissue (BAT) and in white epididymal adipose tissue of rats acclimated to constant or fluctuating cold. Experiments were carried out on isolated adipocytes or tissue homogenates. In brown or white adipose tissue or isolated adipocyte homogenates, two different apparent Km values were found according to the substrate (cAMP) concentration. The low Km was at about 10(-6) M and the high one at about 10(-4) M. The apparent V of the high Km enzyme was about 10-fold higher than the V of the low Km enzyme. Cold acclimation to constant or fluctuating cold did not modify appreciably the Km or V values. For low substrate concentrations (10(-6)-10(-8) M), the specific activity of PDE expressed per milligram of protein was decreased in BAT adipocytes of the two groups of cold-acclimated rats, compared to controls. Inversely, it was increased in total tissue homogenates. These variations were smaller in fluctuating cold than in constant cold-acclimate rats. They could, in part, induce the increases in lipolysis and in blood flow observed in the BAT of cold-acclimated rats.
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PMID:3':5'-Cyclic-AMP phosphodiesterase activities in white and brown adipose tissues of cold-acclimated rats. 17 98

Cyclic nucleotide phosphodiesterase activity of several tissues of rat is inhibited by an endogenous factor isolated from rat adipocytes following exposure of these cells to agents that raise intracellular cyclic AMP levels. The inhibitory action was demonstrated with varying cAMP concentrations from 0.1-400 muM. Enzyme from 10,000 X g supernatant of epididymal adipose tissue was inhibited approximately 2-3 fold more than the plasma membrane of adipocytes by a given concentration of the feedback regulator. Kinetic analysis of cAMP phosphodiesterase of plasma membrane showed that feedback regulator (8.8 U/ml) inhibited the Vmax 48%. The maximum inhibition of phosphodiesterase by feedback regulator (20 U/ml) was about 80%. The apparent Km for cAMP was increased. The ability of phosphodiesterase from several tissues of rat (10,000 X g supernatant) to hydrolyze cAMP and cGMP was tested. Feedback regulator inhibited cGMP hydrolysis in cardiac muscle and 5 other tissues 23-92% more than it inhibited the hydrolysis of cAMP. The physiological significance of this inhibitory effect can begin to be clarified when the feedback regulator is purified to homogeneity and characterized.
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PMID:Inhibition of cyclic nucleotide phosphodiesterase activity by an endogenous factor. 17 58

In non-obese but diabetic 15-week-old KK mice which showed fatty liver histopathologically, the content of liver lipids and the levels of blood glucose and plasma IRI were greater than those in the control ICR mice of the same age and were quite similar to those in GTG-obese mice. In 6-week-old KK mice which excreted no glycosuria and showed normal hepatic tissues, only plasma IRI level was slightly elevated as compared with that in the control mice. The cyclic 3',5'-AMP stimulators like epinephrine and theophylline exerted far less potent stimulatory effects on lipolytic activity in 6-week-old KK mice than in the control mice, as in diabetic 15-week-old KK mice and GTG-obese mice. Theophylline potentiated the lipolytic effect of epinephrine lineraly in KK mice, the tendency being different from that in the control mice, and only the submaximal rate was obtained. Furthermore, the inhibitory effect of theophylline on PDE from the epididymal adipose tissue was less potent in 6-week-old KK mice than in healthy ICR mice of the same age.
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PMID:Effects of epinephrine and theophylline on lipolytic response in hereditary diabetic mice. 18 66

The effect of elevated body temperatures on the concentrations of epididymal cyclic AMP levels in non-diabetic, diabetic and hypophysectomized rats was studied. Cyclic AMP levels were increased during hyperthermia in all animals examined. This increase in epididymal cyclic AMP concentration was not seen in animals that had been supplemented with exogenous insulin prior to the experiment. The effect of pituitary lipolytic hormones on epididymal cyclic AMP levels was also investigated. Significant elevations of epididymal cyclic AMP levels were observed in hypophysectomized rats during hyperthermia indicating that pituitary hormones are not essential in causing these increases. Extrapituitary hormones, such as glucagon, might be responsible for epididymal cyclic AMP increases. Increases in epididymal cyclic AMP levels may therefore be the result of the reduction of blood insulin and concomitant increases of lipolytic hormones of both pituitary and extrapituitary origins.
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PMID:Effect of hyperthermia on epididymal cyclic AMP levels in diabetic non-diabetic and hypophysectomized rats. 19 89

Two compounds, theophylline and 8-aza-9-furfuryl-adenine (SQ 4665), were found to maximally stimulate lipolysis in preparations of rat epididymal fat cells in the absence of exogenous hormones. Cyclic AMP levels in lipocytes maximally stimulated by either agent alone were unchanged from control levels. In contrast, lipolysis stimulated by either epinephrine alone or in combination with several cyclic nucleotide phosphodiesterase inhibitors correlated well with increases in the levels of cyclic AMP observed. These results suggest the presence of a non-cyclic AMP dependent pathway for the stimulation of lipolysis in rat epididymal fat cells.
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PMID:Dissociation of lipolysis from the levels of cyclic AMP in rat epididymal fat cells. 19 20

The present study reports the effects on lipolysis occurring in isolated rat epididymal adipocytes of several agents which have each been found to interfere with membrane calcium transport in a variety of tissues. As reported by other workers, the local tetracaine was a strong inhibitor of hormone accelerated but not of basal lipolysis. The bivalent cations Mn2+ and Co2+ were similarly found to inhibit lipolysis stimulated with either epinephrine, ACTH, theophylline or dibutyryl cyclic AMP, whereas basal lipolysis was not markedly altered. This effect of Mn2+ and Co2+ was not mimicked by either Sr2+, Ba2+, Mg2+ or Ca2+. Cyclic AMP levels in adipocytes stimulated with epinephrine or ACTH tended to be higher in the presence of Mn2+ and Co2+. It is concluded, therefore, that Mn2+ and Co2+ inhibit lipolysis by uncoupling cyclic AMP accumulation from activation of triglyceride lipase. In contrast to Mn2+ and Co2+, the calcium antagonists La3+ and D600 were without effect on lipolysis. The antilipolytic effect of tetracaine, Mn2+ and Co2+ was found to persist in the absence of extracellular calcium, suggesting therefore that the antilipolytic effect of these drugs is unrelated to inhibition of calcium influx into adipocytes. The possibility is discussed that lipolytic agents cause an intracellular redistribution of calcium ion and that local anesthetics, Mn2+ and Co2+ interfere with lipolysis by preventing this intracellular redistribution of calcium.
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PMID:Calcium antagonists and lipolysis in isolated rat epididymal adipocytes: effects of tetracaine, manganese, cobaltous and lanthanum ions and D600. 20 97


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