title: Studies on the microsoml sodium-plus-potassium ion-stimulated adenosine triphosphatase system in rat ventral prostate.
abstract: A Mg(2+)+Na(+)+K(+)-stimulated adenosine triphosphatase (ATPase) preparation was isolated from rat ventral prostate by flotation of microsomal membranes in high-density sucrose solutions. The reaction medium for optimum Na(+)+K(+)-stimulated ATPase activity was found to be: Na(+), 115mm; K(+), 7-10mm; Mg(2+), 3mm; ATP, 3mm; tris buffer, pH7.4 at 38 degrees , 20mm. The average DeltaP(i) (Mg(2+)+Na(+)+K(+) minus Mg(2+)+Na(+)) was 9mumoles/mg. of protein/hr., representing a 30% increase over the Mg(2+)+Na(+)-stimulated ATPase activity. At high concentrations, K(+) was inhibitory to the enzyme activity. Half-maximal inhibition of Na(+)+K(+)-stimulated ATPase activity was elicited by ouabain at 0.1mm. The preparation exhibited phosphatase activity towards ribonucleoside triphosphates other than ATP. However, stimulation of P(i) release by Na(+)+K(+) was observed only with ATP as substrate. The apparent K(m) for ATP for Na(+)+K(+)-stimulated activity was about 0.3x10(-3)m. Ca(2+) inhibited only the Na(+)+K(+)-stimulated ATPase activity. Mg(2+) could be replaced by Ca(2+) but then no Na(+)+K(+) stimulation of ATPase activity was noticed. The addition of testosterone or dihydrotestosterone (17beta-hydroxy-5alpha-androstan-3-one) in vitro at 0.1-10mum under a variety of experimental conditions did not significantly increase the Na(+)+K(+)-stimulated ATPase activity. The enzyme preparations from prostates of orchidectomized rats, however, exhibited a drastic decrease in the specific activity of Na(+)+K(+)-stimulated ATPase; these changes were prevented in the orchidectomized rats by injection of testosterone propionate.
mesh_terms: D000251:Adenosine Triphosphatases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000818:Animals; D002118:Calcium; D002369:Castration; D002499:Centrifugation, Density Gradient; D066298:In Vitro Techniques; D008274:Magnesium; D008297:Male; D008861:Microsomes / Q000201:enzymology*; D010042:Ouabain / Q000494:pharmacology; D011188:Potassium; D011467:Prostate / Q000201:enzymology*; D051381:Rats; D012964:Sodium; D013096:Spermine; D013739:Testosterone / Q000494:pharmacology
chemical_list: D013096:Spermine; D013739:Testosterone; D010042:Ouabain; D012964:Sodium; D000251:Adenosine Triphosphatases; D008274:Magnesium; D011188:Potassium; D002118:Calcium