title: Calcium transport by bull spermatozoa plasma membranes.
abstract: Plasma membrane isolated from frozen ejaculated bull spermatozoa were found to contain calcium transport activity. Thin-section electronmicrography of these membranes revealed relatively homogeneous vesicular membranes with sizes ranging from 2000 to 6000 A in diameter. Membrane vesicles that were exposed to oxalate as a calcium-trapping agent accumulated Ca2+ in the presence of Mg2+ and ATP. One microM of the calcium-ionophore A23187, added initially, completely inhibited net Ca2+ uptake and, if added later, caused the release of Ca2+ accumulated previously. An Arrhenius plot for the rate of Ca2+ uptake revealed a break at 32--33 degrees C, and Ea of 4.4 kcal/mol above the break and 32.2 kcal/mol below. The Ca+ uptake was inhibited by low concentrations of quercetin, which is known to be an inhibitor of (Ca2+ + Mg2+)-ATPase in many systems.
mesh_terms: D000818:Animals; D001693:Biological Transport, Active / Q000187:drug effects; D017301:Ca(2+) Mg(2+)-ATPase; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000378:metabolism*; D002151:Calorimetry; D002417:Cattle; D002462:Cell Membrane / Q000201:enzymology / Q000648:ultrastructure; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology; D008297:Male; D008854:Microscopy, Electron; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism; D013094:Spermatozoa / Q000201:enzymology* / Q000648:ultrastructure
chemical_list: D000001:Calcimycin; D017301:Ca(2+) Mg(2+)-ATPase; D000252:Calcium-Transporting ATPases; D000254:Sodium-Potassium-Exchanging ATPase; D008274:Magnesium; D002118:Calcium