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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

Rabbit spermatozoa from the cauda epididymis produced 0.7-0.8nmol of H(2)O(2)/min per 10(8) cells at cell concentrations below 10(7) cells/ml with linear dependence on cell concentration. Above 2 x 10(7) cells/ml, the rate again became linear with cell concentration but decreased to 0.1-0.2nmol/min per 10(8) cells. Spermatozoa treated with amphotericin B, which makes the plasma membrane highly permeable to low-molecular-weight compounds, showed a similar dependence of H(2)O(2) production rate on cell concentration; below 10(7) cells/ml the rate was 0.3-0.4nmol/min per 10(8) cells; above 2 x 10(7) cells/ml, the rate was 0.1-0.2nmol/min per 10(8) cells. Hypo-osmotically treated rabbit epididymal spermatozoa, a preparation useful for studying mitochondrial function in sperm [Keyhani & Storey (1973) Biochim. Biophys. Acta305, 557-565] produced 0.1-0.2nmol/min per 10(8) cells in the absence of added substrates. The dependence of rate on cell concentration was linear from 10(7) to 2.2 x 10(8) cells/ml. This endogenous rate was unaffected by rotenone, but stimulated 4-fold by antimycin A. Addition of the mitochondrial substrates lactate plus malate increased the rate of H(2)O(2) production to 0.3nmol/min per 10(8) cells. The decreased rate of H(2)O(2) production observed with intact sperm at high cell concentrations is attributed to reaction of H(2)O(2) with the cells, possibly with the plasma membrane, which is lost after hypo-osmotic treatment. Rabbit spermatozoa have glutathione peroxidase and glutathione reductase activities, but these seem to play little role in removal of H(2)O(2) generated. The rate at low cell concentration is taken to be the unperturbed rate. The sources of H(2)O(2) production in rabbit spermatozoa have been tentatively resolved into a low-molecular-weight component, lost after amphotericin treatment, a mitochondrial component and a rotenone-insensitive component that has not been identified.
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PMID:Oxygen metabolism of mammalian spermatozoa. Generation of hydrogen peroxide by rabbit epididymal spermatozoa. 732 6

Hypotonic resistance of boar spermatozoa was investigated by measuring the ratio of live/dead spermatozoa (SYBR-14/propidium iodide) by flow cytometry after hypotonic stress. The survival rate of ejaculated spermatozoa incubated in hypotonic solutions ranging from 3 to 330 mmol/kg followed a sigmoid curve that fitted a simple logistic model. The critical osmolality value (Osm(crit)) at which 50% of spermatozoa died was determined with this model. Hypotonic resistance of spermatozoa increased with temperature between 15 and 39 degrees C and decreased after hydrogen superoxide treatment, but was not modified during 8 days of preservation in Beltsville thawing solution. Hypotonic resistance markedly decreased during epididymal maturation and after ejaculation as Osm(crit) at 15 degrees C was 54.7+/-3.2, 68.5+/-10.6, 116.7+/-2.1 and 194.3+/-3.7 mmol/kg for the caput, corpus, cauda and ejaculated spermatozoa respectively. Hypo-osmotic stress of 100 mmol/kg revealed a sperm subpopulation exhibiting increased hypotonic resistance compared with the whole ejaculate (Osm(crit)=67.8+/-2.1 mmol/kg). Consistent differences were observed between lean and standard breeds (Pietrain versus Large White) and between boars within the same breed. According to data collected by artificial insemination centers during a large-scale field trial, hypotonic resistance of ejaculates was found to be positively correlated with in vivo fertility.
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PMID:Hypotonic resistance of boar spermatozoa: sperm subpopulations and relationship with epididymal maturation and fertility. 1899 73