Regulation of (Ca2+-Mg2+)-ATPase activity by calcitonin binding to rat liver plasma membranes.
The plasma membranes isolated from rat liver bound 125I-labelled ([125I]) synthetic [Asu1,7]eel calcitonin (CT), with increasing concentrations of [125I]CT. This specific binding was completely saturated at a concentration of 0.5 nM CT. A high affinity Ca2+-stimulated, Mg2+-dependent ATPase [(Ca2+-Mg2+)-ATPase] activity in the plasma membranes was significantly decreased by the presence of a very low concentration of CT (7.4 pM), although the hormone did not affect the activity of the plasma membrane 5'-nucleotidase. The concentration of CT needed for maximal inhibition of (Ca2+-Mg2+)-ATPase in the plasma membranes was less than 0.74 nM. The plasma membranes washed with 10(-3)% digitonin did not show an inhibitory effect of CT on (Ca2+-Mg2+)-ATPase activity, while the reagent did not have a significant effect on the enzyme. These results suggest that the inhibition of (Ca2+-Mg2+)-ATPase activity may be part of the mechanism by which CT elevates cytosolic Ca2+ in liver cells.
D000804:Angiotensin II / Q000494:pharmacology; D000818:Animals; D017301:Ca(2+) Mg(2+)-ATPase; D002116:Calcitonin / Q000031:analogs & derivatives / Q000378:metabolism* / Q000494:pharmacology; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D002462:Cell Membrane / Q000201:enzymology; D004072:Digitonin / Q000494:pharmacology; D004837:Epinephrine / Q000494:pharmacology; D005934:Glucagon / Q000494:pharmacology; D007328:Insulin / Q000494:pharmacology; D008099:Liver / Q000201:enzymology*; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D018003:Receptors, Calcitonin; D011956:Receptors, Cell Surface / Q000378:metabolism
D007328:Insulin; D018003:Receptors, Calcitonin; D011956:Receptors, Cell Surface; D000804:Angiotensin II; D002116:Calcitonin; D005934:Glucagon; D017301:Ca(2+) Mg(2+)-ATPase; D000252:Calcium-Transporting ATPases; D004072:Digitonin; C012755:elcatonin; D004837:Epinephrine