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

Several lines of evidence have demonstrated conclusively the presence of cAMP-dependent protein kinase (ecto-RC) activity on the external surface of goat cauda-epididymal intact spermatozoa. The intact-cell ecto-kinase that caused transfer of the terminal phosphate of exogenous ATP to the serine and threonine residues of exogenous histone was specifically activated by cAMP. As well, the ecto-kinase caused phosphorylation of the synthetic peptide Kemptide. The isolated spermatozoa, before or after incubation with reaction mixture for ecto-kinase assays, were approximately 99.5% viable, as shown by the analyses of ethidium bromide fluorescence and the cytosolic marker enzymes lactic dehydrogenase and 3-phosphoglycerate kinase. The ecto-kinase activity was not due to contamination of epididymal plasma and damaged cells or to protein kinase that may have leaked from the cells. There was little uptake of ATP and histone by the cells. The intact-cell kinase activity was strongly (80-90%) inhibited by treatment with membrane nonpenetrating surface probes: p-chloromercuriphenylsulfonic acid (2 microM), diazonium salt of sulfanilic acid (DSS, 0.5 mM), and proteases such as trypsin, chymotrypsin, and pronase (each 125 micrograms/mL). Disruption of sperm plasma membrane by sonication or Triton X-100 (0.2%) caused about a fivefold increase of the intact sperm kinase activity. Highly purified sperm plasma membrane (PM) possessed ecto-kinase activity that was resolved into type I and II kinases by DEAE-cellulose chromatography, the type I isoenzyme being the major (approximately 70%) enzymic species. Treatment of the intact spermatozoa with DSS prior to isolation of PM caused a marked loss of the activities of both the isoenzymes, indicating thereby the "ecto" nature of the PM-bound type I and II kinases. Preparations of vigorously forward-motile spermatozoa with 100% intactness had approximately fourfold higher specific activity of the ecto-kinase than the "composite" cells from which the former cells were isolated. However, the profiles of the type I and II ecto-kinases of the composite, as well as forward-motile spermatozoa, were nearly identical. The data are consistent with the view that ecto-kinases may have role in the regulation of flagellar motility.
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PMID:Type I and II cAMP-dependent ecto-protein kinases in goat epididymal spermatozoa and their enriched activities in forward-motile spermatozoa. 216 Aug 33

Goat cauda-epididymal intact sperm ecto [32P] proteins phosphorylated in presence of exogenous [gamma-32P]ATP by an endogenous ecto-cyclic AMP-independent protein kinase (CIK), have been found to lose 32P when the labelled cells are incubated at 37 degrees C in a modified Ringer's solution. Analysis of the 32P-labelled products of the turnover of the ecto-phosphoproteins show that 32Pi rather than 32P-labelled peptides, is released from the cell-surface phosphoproteins indicating that the turnover of the ecto-phosphoproteins is mediated by an endogenous sperm outer-surface phosphoprotein phosphatase (ecto-PPase). The ecto-PPase is not a non-specific phosphatase since unlabelled p-nitrophenyl phosphate, beta-glycerophosphate or ATP at a relatively high concentration (1 mM each) has no appreciable effect on the dephosphorylation of the cell-surface proteins. The intact-sperm ecto-proteins phosphorylated and then dephosphorylated by the endogenous ecto-CIK and PPase respectively, undergo rephosphorylation by the cell-surface CIK. The data are consistent with the view that sperm external surface possesses a novel coupled-ecto-CIK and PPase enzyme system that regulates the phosphorylated states of the intact-sperm ecto-proteins by a cyclic mechanism of protein phosphorylation and dephosphorylation.
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PMID:Occurrence of a coupled-enzyme system on the intact-sperm outer surface that phosphorylates and dephosphorylates ecto-proteins. 216 95

1. The effects of ATP and some of its more stable analogues have been examined upon preparations of epididymal and prostatic halves of vasa deferentia and of cauda epididymides from rats that had undergone vasectomy by medial transection of the vas deferens. 2. After unilateral vasectomy, the potencies of ATP, beta, gamma-methylene ATP and 5'-adenylylimidodiphosphate (AppNHp) in tissues ipsilateral to the vasectomy were decreased compared to tissues from the contralateral unoperated side of the animal. 3. Tissues from bilaterally vasectomized rats were less responsive to ATP when compared to tissues taken from sham-operated rats. 4. Tissues taken from rats which had undergone vasovasostomies following unilateral vasectomy remained less responsive to these purines. 5. Responses of cauda epididymides and epididymal halves of vasa deferentia taken from unilaterally and bilaterally vasectomized rats to alpha, beta-methylene ATP usually did not differ from those of respective controls. 6. It is proposed that the subsensitivity which develops to ATP and some of its analogues on the epididymis and vas deferens following vasectomy may reflect increased breakdown, perhaps associated with changes in structural integrity of the tissues, rather than with the sympathetic denervation which is associated with vasectomy.
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PMID:Subsensitivity to ATP and some analogues in preparations of rat cauda epididymis and vas deferens after vasectomy. 220

A differential response to cholinomimetic agonists in epididymal and prostatic portions of rat vas deferens was characterized. The prostatic portion was less sensitive to acetylcholine and carbachol than the epididymal portion. The contraction induced by cholinomimetic agonists was inhibited in the epididymal portion by atropine (1.0-3.0 nM) and in the prostatic portion by hexamethonium (0.1 mM). The contractile response of the prostatic portion to exogenous acetylcholine was not inhibited by textrodotoxin (1.0 microM) but was attenuated by reserpine treatment (10 mg.kg-1 i.p. 24 h) and by prazosin or alpha, beta-methylene ATP. A combination of an alpha-1-adrenoceptor antagonist (prazosin) and P2 purinoceptor desensitization with alpha, beta-methylene ATP abolished the contractile response of the prostatic portion. The contraction induced by repetitive field stimulation of the prostatic portion was attenuated by hexamethonium whereas the response to a single stimulus was not modified. The data suggest that cholinomimetic drugs activate both nicotinic receptors located in nerve terminals of the prostatic portion and muscarinic receptors located in the smooth muscle cells of the epididymal portion, and that stimulation of nicotinic receptors induces the release of noradrenaline and ATP.
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PMID:Presynaptic nicotinic receptors involved in release of noradrenaline and ATP from the prostatic portion of the rat vas deferens. 221 75

Turnover rates of oxidative energy metabolism were measured as oxygen consumption in untreated and caffeine-stimulated epididymal bull spermatozoa respiring with lactate. Incubation of spermatozoa with 1 mM caffeine led to an increase in respiration of approx. 60%. The rate of uncoupled respiration and the vanadate-insensitive part of oxygen consumption were not affected by caffeine. The small effect of ouabain on respiration (-10%) indicated a minor contribution of Na+/K+-ATPase to the ATP consumption. The major part of ATP turnover was caused by motility shown by the strong linear correlation between respiration and motility in untreated and caffeine-treated spermatozoa. In comparison with ejaculated spermatozoa investigated in a previous study, epididymal cells exhibited the same rates of uncoupled and ouabain-sensitive respiration. The efficiency of transforming mitochondrially-produced ATP into cell motion was the same in epididymal and ejaculated spermatozoa. The ATP-producing capacity of sperm mitochondria was utilized in untreated epididymal, in caffeine-stimulated epididymal and in ejaculated spermatozoa, by 20-25%, 40-45% and 45-50%, respectively. The results showed that the capacity of mitochondrial. ATP formation remains unchanged after ejaculation and is utilized to a higher extent by stimulated motility. Treatment with caffeine affected epididymal spermatozoa in a similar manner.
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PMID:Quantification of aerobic energy turnover in epididymal bull spermatozoa. 229 10

Calcium uptake into bovine epididymal spermatozoa is enhanced by introducing phosphate in the suspending medium (Babcock et al. (1975) J. Biol. Chem. 250, 6488-6495). This effect of phosphate is found even at a low extracellular Ca2+ concentrations (i.e., 5 microM) suggesting that phosphate is involved in calcium transport via the plasma membrane. Bicarbonate (2 mM) cannot substitute for phosphate, and a relatively high bicarbonate concentration (20 mM) causes partial inhibition of calcium uptake in absence of Pi. In the presence of 1-2 mM phosphate, 20 mM bicarbonate enhances Ca2+ uptake. The data indicate that the plasma membrane of bovine spermatozoa contains two carriers for Ca2+ transport: a phosphate-independent Ca2+ carrier that is stimulated by bicarbonate and a phosphate-dependent Ca2+ carrier that is inhibited by bicarbonate. Higher phosphate concentrations (i.e., 10 mM) inhibit Ca2+ uptake into intact cells (compared to 1.0 mM phosphate) and this inhibition can be relieved partially by 20 mM bicarbonate. This effect of bicarbonate is inhibited by mersalyl. Calcium uptake into the cells is enhanced by adding exogenous substrates to the medium. There is no correlation between ATP levels in the cells and Ca2+ transport into the cell. ATP levels are high even without added exogenous substrate and this ATP level is almost completely reduced by oligomycin, suggesting that ATP can be synthesized in the mitochondria in the absence of exogenous substrate. Calcium transport into the sperm mitochondria (washed filipin-treated cells) is absolutely dependent upon the presence of phosphate and mitochondrial substrate. Bicarbonate cannot support Ca2+ transport into sperm mitochondria. There is good correlation between Ca2+ uptake into intact epididymal sperm and into sperm mitochondria with the various substrates used. This indicates that the rate of calcium transport into the cells is determined by the rate of mitochondrial Ca2+ uptake and respiration with the various substrates.
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PMID:Regulation of calcium transport in bovine spermatozoa. 239 22

1 Capsaicin (Cap) enhanced the twitch response of the epididymal and prostatic portions of rat vas deferens induced by field stimulation at 0.1 Hz. The effect of Cap was reproducible and showed no desensitization. 2 Prazosin, and pretreatment with reserpine or Cap did not affect the potentiating effect of Cap, whereas pretreatment with 6-hydroxydopamine abolished the action of Cap. 3 Cap tended to attenuate the contractions induced by noradrenaline, tyramine and ATP. 4 Like Cap, substance K and substance P augmented the twitch response without causing desensitization, but their effects differed somewhat from that of Cap. Calcitonin gene-related peptide inhibited the twitch response. 5 These results suggest that Cap enhances a stimulation-induced, prazosin-resistant non-adrenergic twitch response of rat vas deferens through an as yet undefined prejunctional mechanism. This mechanism is possibly mediated by some peptide released in response to Cap from sensory neurones, which in turn acts on sympathetic nerves and increases stimulation-induced release of a mediator or cotransmitter responsible for the non-adrenergic twitch response. However, the possibility that Cap has a direct action on sympathetic nerves cannot be ruled out.
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PMID:Capsaicin enhances the non-adrenergic twitch response of rat vas deferens. 244 7

Capacitation of hamster caudal spermatozoa at a density of 1 x 10(6)/ml is associated with a progressive rise in cAMP levels that precedes the onset of hyperactivated motility. This increase is not expressed by caput spermatozoa incubated under identical conditions. Both the incidence of hyperactivation and the rise in cAMP levels are severely attenuated in the absence of exogenous calcium. Neither factor is restored to control levels by the addition of the phosphodiesterase inhibitor IBMX, although in the presence of exogenous calcium, this reagent increased cAMP levels, stimulated percentage motility and advanced the appearance of hyperactivation. Treatment of spermatozoa at a density of 1 x 10(6)/ml with the calmodulin antagonist, calmidazolium (CZ), caused severe disruption of sperm motility and abolished hyperactivation, while causing only a slight reduction in cAMP content. Addition of IBMX in the presence of CZ elevated cAMP content to levels higher than normally observed during capacitation but did not restore either coordinated or hyperactivated motility. To determine both the mechanisms responsible for this elevation of cAMP content and the changes that occur during epididymal maturation to facilitate the expression of this increase, the free cytosolic calcium concentration, ATP levels, and intracellular pH of caput and caudal cells were compared. The calcium content of caudal spermatozoa rose significantly at a time when cAMP levels were increasing, while ATP content and intracellular pH fell. However, the inability of caput spermatozoa to express a rise in cAMP content was not due to deficiencies in any of these factors. These results indicate a positive role for the cAMP rise in the expression of hyperactivated motility and that the fundamental control mechanism governing both these events may be the influx of calcium that accompanies capacitation in this species.
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PMID:Relationship between calcium, cyclic AMP, ATP, and intracellular pH and the capacity of hamster spermatozoa to express hyperactivated motility. 254 81

Responses of rat isolated vas deferens to electrical stimulation through field electrodes (400 mA, 1 ms duration, single shocks at 5 min intervals) were potentiated by meptazinol (10 to 300 microM) in whole tissues and also in the separated prostatic and epididymal portions. The effect was fast in onset, reproducible and easily reversed by washing. Prazosin (0.1 microM) practically abolished the response of the epididymal portion to electrical stimulation while the response of the prostatic portion was only slightly reduced (less than 20%). In the presence of prazosin, meptazinol still produced potentiation of the response of the prostatic portion. Nifedipine (2 microM) practically abolished the response of the prostatic portion to electrical stimulation while the response of the epididymal portion was only slightly reduced (less than 20%). In the presence of nifedipine, meptazinol no longer produced potentiation of the response of the epididymal portion. Exogenous ATP (5 microM to 1 mM) and phenylephrine (1 to 50 microM) produced a contractile response which was potentiated in the presence of meptazinol (100 microM) but in the presence of meptazinol (100 microM) and nifedipine (5 mM) together, potentiation of phenylephrine no longer occurred. It is suggested that potentiation by meptazinol of electrically induced responses in this tissue is due to a direct action on the smooth muscle.
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PMID:Effect of meptazinol on evoked responses in rat vas deferens. 257 44

Carbachol (0.1-300 mumol/L) potentiated contractions to field stimulation (0.1 Hz, 1 ms, supramaximal V) in the rat epididymal and prostatic vas deferens. Desensitization of P2-purinoceptors by exposure to alpha,beta-methylene ATP (30 mumol/L) markedly reduced (greater than 80%) the potentiating effect of carbachol in the prostatic vas deferens but only moderately reduced (about 20%) the maximal stimulated response to carbachol in the epididymal segment. The presence of prazosin (10 mumol/L) and yohimbine (10 mumol/L), being selective alpha 1- and alpha 2-adrenoceptor antagonists, did not modify the attenuation of carbachol potentiation caused by alpha,beta-methylene ATP treatment. At 0.1 mmol/L, alpha,beta-methylene ATP had no significant effect on the binding of [3H]QNB to muscarinic cholinergic receptors. It is concluded that carbachol may potentiate the contractions to field stimulation in the prostatic vas deferens via an enhancement of purinergic neurotransmission. The molecular mechanism of carbachol potentiation in the epididymal vas deferens remains to be established.
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PMID:Effects of alpha,beta-methylene ATP on potentiation of contractions to field stimulation of rat vas deferens by carbachol. 281 95


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