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Query: UNIPROT:P56851 (epididymal)
 11,273 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Nitric oxide gas (NO) increased guanylate cyclase [GTP pyrophosphate-lyase (cyclizing), EC 4.6.1.2] activity in soluble and particulate preparations from various tissues. The effect was dose-dependent and was observed with all tissue preparations examined. The extent of activation was variable among different tissue preparations and was greatest (19- to 33-fold) with supernatant fractions of homogenates from liver, lung, tracheal smooth muscle, heart, kidney, cerebral cortex, and cerebellum. Smaller effects (5- to 14-fold) were observed with supernatant fractions from skeletal muscle, spleen, intestinal muscle, adrenal, and epididymal fat. Activation was also observed with partially purified preparations of guanylate cyclase. Activation of rat liver supernatant preparations was augmented slightly with reducing agents, decreased with some oxidizing agents, and greater in a nitrogen than in an oxygen atmosphere. After activation with NO, guanylate cyclase activity decreased with a half-life of 3-4 at 4 degrees but re-exposure to NO resulted in reactivation of preparations. Sodium azide, sodium nitrite, hydroxylamine, and sodium nitroprusside also increased guanylate cyclase activity as reported previously. NO alone and in combination with these agents produced approximately the same degree of maximal activation, suggesting that all of these agents act through a similar mechanism. NO also increased the accumulation of cyclic GMP but not cyclic AMP in incubations of minces from various rat tissues. We propose that various nitro compounds and those capable of forming NO in incubations activate guanylate cyclase through a similar but undefined mechanism. These effects may explain the high activities of guanylate cyclase in certain tissues (e.g., lung and intestinal mucosa) that are exposed to environmental nitro compounds.
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PMID:Nitric oxide activates guanylate cyclase and increases guanosine 3':5'-cyclic monophosphate levels in various tissue preparations. 2 Jun 23

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

The in vitro effects of insulin on different phosphodiesterase activities present in rat epididymal fat cells from normal and hypothyroid rats have been studied. Evidence is presented that insulin increases the maximum velocity of a particulate, low Km, cyclic adenosine-3', 5'-monophosphate (cyclic AMP) phosphodiesterase in both types of cells, this effect being more clearly evident with the fat cells from hypothyroid animals; combination of insulin and thyroidectomy resulted in a 400% stimulation with 10-10 - 10-9 M insulin. A clear and significant effect was apparent at 10-11 M insulin. However, the dose-response curve was biphasic, since stimulation by insulin was suppressed for doses of hormone higher 10-8 - 10-7 M. Moreover, insulin effects were very fast, since clear stimulation was observed after only 2 min of incubation; the maximal increase was obtained after 10 min. Insulin did not significantly affect the soluble cyclic AMP phosphodiesterase activity in normal cells, thus confirming results obtained by others. However, the soluble cyclic AMP phosphodiesterase activity was clearly stimulated by insulin when the fat cells were prepared from hypothyroid rats. Maximal stimulation was obtained with 10-9 M insulin; the response was again very fast. Soluble cyclic GMP phosphodiesterase activity was also increased additively by hypothyroidism and insulin, maximal stimulation being obtained with 10-9 M insulin. With this dose of insulin the additive effects of thyroidectomy and insulin produced a 5-fold stimulation. The effect of insulin on the soluble cyclic GMP phosphodiesterase was very fast (2-5 min). With both soluble cyclic nucleotide phosphodiesterase activities, insulin increased the maximal velocity but not apparent Km of the enzyme. Thus, hypothyroidism and insulin produced additive effects suggesting a different mechanism of action of these two hormonal situations on the degradation of the intracellular pools of cyclic AMP and cyclic GMP.
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PMID:Cyclic nucleotide phosphodiesterases, insulin and thyroid hormones. 18 75

In this work the kinetics of activation of the cyclic AMP-dependent protein kinase by several catecholamines and ACTH, have been studied in rat epididymal fat pads and isolated fat cells. The method of Soderling and co-workers which permits the measurement of the state of activation of the protein kinase after hormonal stimulation in adipose tissue, has been used. Kinetics experiments where norepinephrine was used showed that the results obtained with isolated cells conform to the models of Sutherland and Brostrom and co-workers. Wtih intact tissue, norepinephrine not only stimulates the protein kinase activity measured without exogenous cyclic AMP but also the total activity measured in the presence of cyclic AMP (5 X 10(-6) M); thus the effect of norepinephrine, obtained during incubation of the tissue, and that of cyclic AMP, added to the soluble fraction after incubation, were additive. This effect seems to be of the beta type because it is blocked completely by propranolol. A weak, additive but significant effect was also obtained with epinephrine and isoproterenol but not with ACTH. Neither cyclic GMP nor cyclic IMP seems implicated in this effect. It was shown that stroma vascular cells which are present in the fat pads are not involved. These results suggest that the effects of norepinephrine on the protein kinase of the fat pads cannot be completely explained by the model of Brostrom and colleagues.
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PMID:Additive effects of norepinephrine and cyclic AMP on the activation of the protein kinase from adipose tissue. 18 9

The guanosine 3': 5'-monophosphate (cyclic GMP) level in isolated rat epididymal fat cells increased more than doubled 10 min after addition to the cells of carbamylcholine (10(-6) M) in the presence or absence of epinephrine (5 X 10(-7) M). Addition of carbamylcholine, cyclic GMP or dibutyryl cyclic GMP (10(-9) to 10(-5) M) did not affect glucose oxidation or epinephrine-stimulated lipolysis of the cells. No significant change in the cyclic GMP level was detected 2 min or 10 min after addition of insulin (1 mU/ml) to the cells, when glucose oxidation was stimulated and lipolysis induced by epinephrine was inhibited. These results indicate that the transient increase in the cyclic GMP level in the cells on treatment with carbamylcholine is not sufficient for expression of the effects of insulin.
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PMID:Effect of guanosine 3' : 5'-monophosphate on glucose oxidation and epinephrine-stimulated lipolysis in isolated rat epididymal fat cells. 18 2

Soluble and particulate fractions from extracts of rat epididymal fat cells were shown to exhibit a number of different phosphodiesterase activities, as determined by substrate specificity and sensitivity to activators and inhibitors. These activities were then further characterized following separation by MonoQ fast protein liquid chromatography (FPLC). A cyclic AMP-specific activity, unaffected by the presence of calcium and calmodulin and inhibited by rolipram, was the major soluble phosphodiesterase. This fraction also contained distinct calcium and calmodulin- and cyclic-GMP-stimulated activities. Over 80% of the phosphodiesterase activity in the particulate fraction could be accounted for by an insulin-activated cyclic AMP and cyclic GMP-hydrolysing enzyme, which was sensitive to inhibition by cyclic GMP, SKF 94120, SKF 95654 and cilostamide, and eluted as a single peak during MonoQ chromatography. At 1 microM cyclic AMP, the phosphodiesterase activity in the soluble fraction was about eight times greater than in the particulate fraction. Specific inhibitors to the particulate phosphodiesterase (cilostamide and SKF 95654) were added to incubations of isolated fat cells, and were able to potentiate sub-maximal concentrations of isoproterenol in the stimulation of lipolysis. These inhibitors were also able to reverse the antilipolytic effect of insulin, demonstrating the importance of the particulate phosphodiesterase in insulin action, despite the fact that its activity represents only a small proportion of the total phosphodiesterase activity in fat cells. Inhibitors of the major soluble phosphodiesterase had no effect on lipolysis.
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PMID:Characterization of the cyclic nucleotide phosphodiesterase isoenzymes present in rat epididymal fat cells. 157 Dec 3

Cyclic nucleotide phosphodiesterase in the plasma membranes of bovine epididymal spermatozoa was stimulated by added Ca2+ and calmodulin. The rate of hydrolysis and responsiveness toward calmodulin was greater for cAMP than for cGMP. The kinetic analysis of the activity revealed two forms of phosphodiesterase with apparent Km values of 7.5 and 95 microM for cAMP. Calmodulin stimulated both of the activities by increasing the Vmax without affecting the Km's. The activity response with respect to Ca2+ concentration appears to be biphasic in both the absence and presence of added calmodulin. Trifluoperazine inhibited the Ca2+- and calmodulin-sensitive enzyme activity in a dose-dependent manner. The calmodulin-stimulated phosphodiesterase activity in the sperm plasma membranes can be solubilized and absorbed to a Calmodulin-Sepharose affinity column in the presence of Ca2+.
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PMID:Calmodulin-stimulated cyclic nucleotide phosphodiesterases in plasma membranes of bovine epididymal spermatozoa. 283 7

The particulate, cGMP- and cilostamide-inhibited "low Km" cAMP phosphodiesterase was purified greater than 100,000-fold in good yield (approximately 20%) from bovine omental fat by a procedure similar to that utilized for purification of an analogous enzyme from rat epididymal adipose tissue; ten-fold more enzyme protein (20-30 micrograms) could be prepared from bovine omentum (25 kg) than from rats (approximately 900 fat pads). Kinetic parameters (all similar to those for the rat enzyme) were: for cAMP, Km and Vmax = 0.3 microM and 2.5 mumol/min/mg, respectively; for cGMP, 0.8 microM and 1.6 mumol/min/mg. For inhibition of cAMP hydrolysis, IC50 values were: for cGMP = 0.6 microM and for OPC 3911, milrinone, CI 930, 0.1-2.0 microM. The purified enzyme, the activity of which eluted from Sephadex G-200 with Mr(app) = 110,000 and was associated with a single protein band during non-denaturing electrophoresis, exhibited on SDS-PAGE silverstained bands of 62 (probably a 61-63 doublet) and 77 kDa, perhaps due to proteolytic nicking. On Western blots, each of the polypeptides cross-reacted with a monoclonal antibody toward the bovine cardiac low Km cAMP and polyclonal rabbit antibody generated toward the purified bovine omental phosphodiesterase. Rabbit anti-phosphodiesterase IgG, which inhibited bovine and rat phosphodiesterase enzymatic activity, did not cross-react with purified bovine retina cGMP-binding or bovine cGMP-stimulated phosphodiesterase.
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PMID:Purification, properties and polyclonal antibodies for the particulate, low Km cAMP phosphodiesterase from bovine adipose tissue. 285 60

The photoaffinity analog [32P]8-N3 cAMP (8-azido adenosine 3',5'-monophosphate was used to analyze the membrane sidedness of rat sperm cAMP binding proteins during epididymal maturation. Evidence is presented here which supports the hypothesis that 35-45% of the regulatory subunits of the Type I and Type II cAMP-dependent protein kinases are readily available to externally added cyclic nucleotide. It was observed by sodium dodecyl sulfate gel electrophoresis (SDS-PAGE) and autoradiography that only two rat sperm proteins (Mr = 49K and 55K) were photolabeled which comigrated on gels with partially purified Type I and Type II regulatory subunits, respectively. Both of these photolabeled epididymal sperm proteins were saturated at physiological titers of [32P]8-N3cAMP and photoincorporation of [32P]8-N3 cAMP was specific since other SDS-resolvable sperm proteins did not photoincorporate the analog. Caput and cauda sperm protein photoincorporation could be effectively blocked by low levels of cAMP, but not by cGMP, ATP or GTP. Sperm epididymal maturation coincided with changes in the cAMP-dependent protein kinase subunits since cauda sperm contained more available Type II than did caput sperm. A subcellular analysis of cAMP-dependent protein kinase regulatory subunit in head and tail fractions was done for caput and cauda sperm and demonstrated that the tail fractions showed more photo-labeling of both Type I and II regulatory subunits than did the head fractions.
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PMID:A study of rat epididymal sperm adenosine 3',5'-monophosphate-dependent protein kinases: maturation differences and cellular location. 298 32

Fat cells from epididymal adipose tissue from normal and streptozotocin-diabetic rats were studied to determine glucose utilization and cyclic nucleotide levels. Diabetic rat fat cells present a higher cAMP content (P less than 0.05) compared with controls. Addition of insulin decreases within 10-min incubation the cAMP content in both normal and diabetic cells (P less than 0.05). However, the value obtained in the latter remains by 25% higher than that of normal cells not exposed to insulin. No changes in cGMP were detected. Pretreatment of the diabetic animals during two days with propranolol (1 mg kg body wt-1 day-1) induces the decrease to normal levels of the fat cell cAMP content. However, it persists the impairment on glucose utilization observed in fat cells from diabetic animals. It seems that the increase in the intracellular amount of cAMP found in fat cells from diabetic rats is not involved, at least directly, to the impaired glucose utilization found in the diabetic state. Furthermore, through an unknown mechanism, pretreatment with propranolol can induce a drop in fat tissue cAMP toward normal values without normalizing glucose utilization.
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PMID:Cyclic AMP, cyclic GMP and glucose utilization by diabetic rat fat cells. 619 78


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