Ca2+-dependent ATPases in the basolateral membrane of rat kidney cortex.
The basolateral segment of the rat renal tubular plasma membrane possesses Ca2+-dependent ATPase activity which was independent of Mg2+. Two kinetic forms were found: one, was a high affinity (apparent Km for free Ca2+ of 172 nM) low capacity (Vmax of 144 nmol of Pi X min-1 mg-1 protein) type; the other, had low affinity (apparent Km of 25 microM) and high capacity (896 nmol of Pi X min-1 X mg-1 protein). Mg2+ inhibited both Ca2+-ATPases. The high affinity enzyme exhibited positive cooperativity with respect to ATP, with a n value of 1.6. Ca2+-ATPase activity was not affected by calmodulin and was not inhibited by vanadate. On the other hand, both high and low affinity Ca2+-ATPase activities were increased when 1,25-dihydroxycholecalciferol was given to vitamin D-deficient rats. Kinetically, the enhanced activities were due to an increase in the Vmax values; the apparent affinities for free Ca2+ were not changed. The physiological function of the vitamin D-sensitive, Mg+-independent, Ca2+-ATPase activities remains to be established.
Y
Y
Tsukamoto
W N
WN
Suki
C T
CT
Liang
B
B
Sacktor
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001485:Basement Membrane / Q000201:enzymology; D002117:Calcitriol / Q000494:pharmacology; D000252:Calcium-Transporting ATPases / Q000378:metabolism*; D006868:Hydrolysis; D007672:Kidney Cortex / Q000648:ultrastructure*; D007700:Kinetics; D008274:Magnesium / Q000378:metabolism; D008297:Male; D009840:Oligomycins / Q000494:pharmacology; D010042:Ouabain / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D012430:Ruthenium Red / Q000494:pharmacology; D013806:Theophylline / Q000494:pharmacology; D014638:Vanadates; D014639:Vanadium / Q000494:pharmacology; D014808:Vitamin D Deficiency / Q000378:metabolism
D009840:Oligomycins; D014639:Vanadium; D012430:Ruthenium Red; D014638:Vanadates; D010042:Ouabain; D000255:Adenosine Triphosphate; D013806:Theophylline; D000252:Calcium-Transporting ATPases; D002117:Calcitriol; D008274:Magnesium