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

Mature rabbit spermatozoa from the cauda epididymidis suspended in potassium Tris phosphate buffer at 24 degrees C produced O2.-, as measured by reduction of acetylated ferricytochrome c, with an intrinsic rate of 0.20 nmol/min per 10(8) cells. This rate increased to 1.80 nmol/min per 10(8) cells in the presence of 10 mM cyanide. These spermatozoa contain 2.8 units per 10(8) cells of superoxide dismutase activity, 95% of which is sensitive, and 5% of which is insensitive, to cyanide inhibition. These activities correspond to the cytosolic Cu-Zn form and the mitochondrial Mn form of the dismutase, respectively. Only the cyanide-sensitive form is released from the sperm on hypo-osmotic treatment or sonication. Hypo-osmotically treated rabbit epididymal spermatozoa produced O2.- with an intrinsic rate of 0.24 nmol/min per 10(8) cells, which increased to 0.58 nmol/min per 10(8) cells in the presence of 10 mM cyanide. Both intact and hypo-osmotically treated cells react with O2.- in a second order reaction as inferred from the hyperbolic dependence on cell concentration of O2.- production rate in both the absence and presence of cyanide. The second order rate constant for this reaction with intact cells, kS, was calculated to be 22.9 X 10(-8) (cells/ml)-1 min-1 in its absence. For hypo-osmotically treated cells, the values of kS were 10.8 X 10(-8) (cells/ml)-1 min-1 and 8.2 X 10(-8) (cells/ml) -1 min-1, respectively. Since hypo-osmotically treated cells have lost much of their plasma membrane, the lower value of kS for the treated cells implies that this membrane is one site of reaction of O2.- with the cells. The increase in kS in the presence of cyanide, which inhibits superoxide dismutase and so increases O2.- production, suggests that the cells become more reactive with O2.- as its production rate increase, as would be expected for the occurrence of radical chain oxidation. This in turn suggests that superoxide dismutase plays a major role in protecting rabbit sperm against damage from lipid peroxidation.
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PMID:Production of superoxide and activity of superoxide dismutase in rabbit epididymal spermatozoa. 629 28

Increases in the amount of the active non-phosphorylated form of pyruvate dehydrogenase in rat epididymal adipose tissue, as a result of incubation with insulin, persist not only during the preparation of mitochondria but also during subsequent incubation of coupled mitochondria in the presence of respiratory substrates. No effect on insulin was found if the hormone was added directly to mitochondria in the presence or absence of added plasma membranes. Concentrations of several possible regulators of pyruvate dehydrogenase kinase (ATP, ADP, NADH, NAD+, acetyl-CoA, CoA and potassium) were measured in rat epididymal-adipose-tissue mitochondria incubated under conditions where differences in pyruvate dehydrogenase activity persist as a result of insulin action. No alterations were found, and it is suggested that inhibition of the kinase is not the principal means by which insulin activates pyruvate dehydrogenase. The intramitochondrial concentration of magnesium was also unaffected. Differences in pyruvate dehydrogenase activity in interscapular brown adipose tissue associated with manipulation of plasma insulin concentrations of cold-adapted rats were also shown to persist during the preparation and subsequent incubation of mitochondria in the presence or absence of GDP. It is pointed out that the persistence of the effect of insulin on pyruvate dehydrogenase in incubated mitochondria will facilitate the recognition of the mechanism of this action of the hormone. Evidence that the short-term action of insulin involves an increase in pyruvate dehydrogenase phosphate phosphatase activity rather than inhibition of that of pyruvate dehydrogenase kinase is discussed.
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PMID:Persistence of the effect of insulin on pyruvate dehydrogenase activity in rat white and brown adipose tissue during the preparation and subsequent incubation of mitochondria. 632 Aug 7

The sensitivity of rat epididymal-adipose-tissue pyruvate dehydrogenase phosphate phosphatase, NAD+-isocitrate dehydrogenase and 2-oxoglutarate dehydrogenase to Ca2+ ions was studied both in mitochondrial extracts and within intact coupled mitochondria. It is concluded that all three enzymes may be activated by increases in the intramitochondrial concentration of Ca2+ and that the distribution of Ca2+ across the mitochondrial inner membrane is determined, as in rat heart mitochondria, by the relative activities of a uniporter (which transports Ca2+ into mitochondria and is inhibited by Mg2+ and Ruthenium Red) and an antiporter (which allows Ca2+ to leave mitochondria in exchange for Na+ and is inhibited by diltiazem). Previous studies with incubated fat-cell mitochondria have indicated that the increases in the amount of active non-phosphorylated pyruvate dehydrogenase in rat epididymal tissue exposed to insulin are the result of activation of pyruvate dehydrogenase phosphate phosphatase. In the present studies, no changes in the activity of the phosphatase were found in extracts of mitochondria, and thus it seemed likely that insulin altered the intramitochondrial concentration of some effector of the phosphatase. Incubation of rat epididymal adipose tissue with medium containing a high concentration of CaCl2 (5mM) was found to increase the active form of pyruvate dehydrogenase to much the same extent as insulin. However, the increases caused by high [Ca2+] in the medium were blocked by Ruthenium Red, whereas those caused by insulin were not. Moreover, whereas the increases resulting from both treatments persisted during the preparation of mitochondria and their subsequent incubation in the absence of Na+, only the increases caused by treatment of the tissue with insulin persisted when the mitochondria were incubated in the presence of Na+ under conditions where the mitochondria are largely depleted of Ca2+. It is concluded that insulin does not act by increasing the intramitochondrial concentration of Ca2+. This conclusion was supported by finding no increases in the activities of the other two Ca2+-responsive intramitochondrial enzymes (NAD+-isocitrate dehydrogenase and 2-oxoglutarate dehydrogenase) in mitochondria prepared from insulin-treated tissue compared with controls.
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PMID:Role of Ca2+ ions in the regulation of intramitochondrial metabolism in rat epididymal adipose tissue. Evidence against a role for Ca2+ in the activation of pyruvate dehydrogenase by insulin. 632 51

When rats are fed a selenium-deficient diet, the glutathione peroxidase activity of epididymal fat-cells decreases to 5-9% of that of control rats fed the same diet supplemented with 0.5 p.p.m. of selenium as sodium selenite. [1-14C]Glucose oxidation in fat-cells from rats fed a selenium-deficient diet is unresponsive to the action of t-butyl hydroperoxide, which stimulates 14CO2 formation from [1-14C]glucose 4-fold in control rats. Insulin enhances [1-14C]glucose oxidation and incorporation into lipids in fat-cells from both groups of rats; however, the response elicited is reduced in fat-cells prepared from selenium-deficient animals. The 'C-1/C-6 ratio' (ratio of glucose C-1 to glucose C-6 oxidized) is enhanced by insulin to a similar degree in fat-cells from both groups of animals. The stimulatory action of Zn2+ and dithiothreitol on [1-14C]glucose oxidation observed in fat-cells from selenium-supplemented rats is greatly reduced in fat-cells from selenium-deficient rats. [1-14C]Glucose oxidation in fat-cells from both groups of animals is highly sensitive to the stimulatory action of adenosine. It is concluded that the enhanced formation and glutathione-linked destruction of H2O2 plays, at the most, only a minor role in the stimulation of the flux of glucose through the pentose phosphate pathway elicited by insulin, although elimination of glutathione peroxidase activity may influence the action of insulin on glucose oxidation. Production and subsequent destruction of H2O2 may play an important role in the stimulatory action of Zn2+ and dithiothreitol on fat-cell [1-14C]glucose oxidation.
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PMID:The effect of selenium-deficiency on rat fat-cell glucose oxidation. 635 53

The effect of adrenalectomy and corticosterone replacement on epididymal enzymes involved in obligatory steps of glycolysis and pentose phosphate pathway were studied along with serum hormonal profiles. Adrenalectomy was found to elevate serum prolactin while the gonadotropins and testosterone were unaltered. In caput epididymal tissue enzymes of the pentose phosphate pathway. Glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase activities were increased after adrenalectomy. However, in corpus epididymal tissue the key enzymes viz. hexokinase, 6-phosphofructokinase and pyruvatekinase of the glycolytic pathway were elevated leaving the pentose phosphate pathway unaffected. Adrenalectomy was also found to favour glycolysis of the epididymal spermatozoa. The possible direct effect of prolactin is discussed to explain the enzymatic changes in epididymis. Corticosterone replacement was found to maintain the enzyme activities along with serum prolactin and corticosterone at control levels. In conclusion, it is suggested that the adrenalectomy induced changes in enzyme activities could be due to the direct effect of prolactin.
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PMID:Effect of adrenalectomy and corticosterone replacement on epididymal carbohydrate metabolism--studies on mature male rats. 640 94

The influence of thyroidectomy on key epididymal enzymes of the Embden-Meyerhof and pentose phosphate pathway have been studied in pubertal and adult animals in relation to the serum hormone profile. Age related differences in the response of epididymal segments were observed with respect to hexokinase activity, although the other 2 key enzymes of the Embden-Meyerhof pathway (6-PFK and PK) were suppressed in all regions of the epididymis in both pubertal and adult rats. The enzymes involved in the pentose phosphate pathway (G-6-PDH and 6-PGDH) remained unaltered. The serum hormone profile revealed that while FSH and testosterone titres were reduced, LH and Prl were unaltered. Replacement of T4 in thyroidectomized animals maintained serum hormone levels and the activities of the enzymes studied at control levels. It is inferred that thyroid hormones may be one part of a complex mechanism that controls carbohydrate metabolism in the epididymis.
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PMID:Influence of hypothyroidism on epididymal enzymes involved in carbohydrate metabolism. Studies in pubertal and adult rats. 641 30

Loss of forward motility of rabbit epididymal spermatozoa in high K+ phosphate buffer is inhibited by taurine, hypotaurine, epinephrine and bovine serum albumin. Pyruvate and lactate also show this effect. The rate of lipid peroxidation in these spermatozoa, as measured by rate of formation of malondialdehyde, is also inhibited by these agents. A close linear correlation between percent inert spermatozoa and malondialdehyde was found, which was independent of the rate of peroxidation. Complete cessation of motility was observed at 0.5 nmol malondialdehyde/10(8) cells in the absence or presence of these agents, which is the same value found in other suspending media in a previous study [Alvarez and Storey (1982) Biol. Reprod. 27:1102-1108]. Albumin was the most effective agent in preventing loss of motility and inhibiting lipid peroxidation. Hypotaurine was the next most effective, followed by taurine, epinephrine, pyruvate and lactate. Hypotaurine reduces the amount of rate of superoxide production, as measured by the rate of reduction of acetylated ferricytochrome c by O(2), from rabbit sperm under these conditions and concomitantly reduces inactivation of the superoxide dismutase in these cells. Since superoxide seems to be the major inducer of lipid peroxidation in rabbit sperm, the protective effect of hypotaurine, which should be readily permeant to the plasma membrane, may be ascribed to scavenging of intracellular superoxide. The mechanism of the protective action of albumin is not known. Rabbit epididymal spermatozoa lose motility over time if Ca2+ or Mg2+ are omitted from the suspending medium.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Taurine, hypotaurine, epinephrine and albumin inhibit lipid peroxidation in rabbit spermatozoa and protect against loss of motility. 662 44

Three isoenzymic species of neutral alpha-mannosidase (I, II and III) were partially purified from rat epididymis and characterized. Calcium phosphate gel preferentially adsorbed acidic alpha-mannosidase activity, thereby removing the acidic enzyme from the neutral mannosidases. The neutral enzymes, which are of cytosolic origin, require Co2+ for activity, and Mn2+ can substitute partially for Co2+. Mg2+ or Ca2+ had little effect on the activity of the isoenzymes, whereas Zn2+ (100 microM) was a potent inhibitor of the mannosidases. The Km values of mannosidases I, II and III for Co2+ were 10, 10 and 2.7 mM respectively. There was marked alteration of the specific activity of the neutral alpha-mannosidases during epididymal development in vivo. The specific activities of mannosidases I and II were relatively high in the young (24 days) rats, and during the subsequent development the specific activities decreased markedly (approx. 2-3-fold). On the contrary, mannosidase III, which showed relatively low specific activity during 24-45 days of age, increased markedly (approx. 2-fold) as the animals reached adulthood.
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PMID:Enzymic characteristics of the isoenzymes of rat epididymal neutral alpha-mannosidases and their changes during development in vivo. 671 26

Nuclear androgen binding sites were examined in late spermatids (stages 12-19) which resisted sonication of homogenized testes of mature male rats. The measurement of unoccupied binding sites in salt extract of purified spermatid heads by nuclear exchange at -10 degrees C was developed and validated. As in the prostate, unoccupied nuclear androgen binding sites in sonicated testes were in low concentration, were not artefactual, and could be occupied both in vivo and in vitro by exogenous androgens, and uniquely in hemicastrated rats by endogenously compensated androgens in the remaining testis. The properties of occupied binding sites in salt extract of purified spermatid heads (measured by nuclear exchange at 4 degrees C for 48 or more hours with 5 nM [3H]dihydrotestosterone) were almost identical to those of occupied binding sites in nuclei of the ventral prostate, except for their concentration. However, levels of specific binding activity approaching 50 fmol/mg DNA could be expected in salt extract of spermatid pellets, by use of a sulfhydryl reducing agent (dithiothreitol) prior to salt extraction, a protease inhibitor (phenylmethylsulfonyl fluoride) in all buffers, and optimization of the sonication protocol. Nuclear androgen binding sites of sonicated epididymal spermatozoa, collected by retrograde perfusion of the cauda epididymidis, were found to be completely salt-resistant. These binding proteins could be extracted by 0.4 M KCl if dithiothreitol and dihydrotestosterone were incorporated into the sonication buffer, if phenylmethylsulfonyl fluoride was added to all buffers, and if the purified epididymal sperm pellet was treated with sarkosyl, a non-ionic detergent, just before salt extraction. The salt extract of epididymal spermatozoa which were treated as described above contained two binding components: a soluble form which was eluted from hydroxylapatite by increasing concentrations of phosphate buffers, and a non-soluble form, free of DNA, which remained in the hydroxylapatite column, and which contained most of the androgen binding sites. Affinity (Kd) of dihydrotestosterone to the soluble and insoluble fractions of the steroid-binding protein complex was determined to be 0.7 and 0.1 nM, respectively. Salt-resistance of binding proteins in germ cells was shown to develop significantly in the last stages of spermiogenesis.
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PMID:Nuclear androgen binding sites in the male rat. III. Late spermatids and spermatozoa in the testis, with an introduction to epididymal spermatozoa. 674 45

1. Increasing concentrations of both Ca2+ and Sr2+ (generated by using EGTA buffers) resulted in 4-fold increases in the initial activity of pyruvate dehydrogenase within intact uncoupled mitochondria from rat epididymal adipose tissue incubated in the presence of the ionophore A23187, ATP, Mg2+ and oligomycin. The k0.5 values (concentrations required for half-maximal effects) for Ca2+ and Sr2+ were 0.54 and 7.1 microM respectively. In extracts of the mitochondria, pyruvate dehydrogenase phosphate phosphatase activity was stimulated about 4-fold by Ca2+ and Sr2+, with k0.5 values of 1.08 and 6.4 microM respectively. 2. NAD+-isocitrate dehydrogenase and oxoglutarate dehydrogenase appeared to be rate-limiting in the oxidation of threo-Ds-isocitrate and oxoglutarate by uncoupled mitochondria from brown adipose tissue of cold-adapted rats. Ca2+ (and Sr2+) diminished the Km for the oxidation of both threo-Ds-isocitrate and oxoglutarate. The kinetic constants for these oxidations were very similar to those obtained for the activities of NAD+-isocitrate dehydrogenase and oxoglutarate dehydrogenase in extracts of the mitochondria. In particular, the k0.5 values for Ca2+ were all in the range 0.2--1.6 microM and Sr2+ was found to mimic Ca2+, but with k0.5 values about 10 times greater. 3. Overall, the results of this study demonstrate that the activities of pyruvate dehydrogenase, NAD+-isocitrate dehydrogenase and oxoglutarate dehydrogenase may all be increased by Ca2+ and Sr2+ within intact mitochondria. In all cases the k0.5 values are close to 1 and 10 microM respectively, as found for the separated enzymes. Experiments on brown-adipose-tissue mitochondria incubated in the presence of albumin suggest that it may be possible to use the sensitivity of the dehydrogenases to Ca2+ as a means of assessing the distribution of Ca2+ across the mitochondrial inner membrane.
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PMID:Role of calcium ions in the regulation of intramitochondrial metabolism. Properties of the Ca2+-sensitive dehydrogenases within intact uncoupled mitochondria from the white and brown adipose tissue of the rat. 677 77


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