Increase of (Ca2++Mg2+)-ATPase activity of renal basolateral membrane by parathyroid hormone via cyclic AMP-dependent membrane phosphorylation.
Studies were made on the mechanism of the effect of parathyroid hormone (PTH) on the activity of (Ca2++Mg2+)-ATPase, a membrane bound Ca2+-extrusion pump enzyme from the basolateral membranes (BLM) of canine kidney (Km for free Ca2+ = 1.3 X 10(-7) M, Vmax = 200 nmol Pi/mg/min). At 1 X 10(-7) M free Ca2+, both PTH (10(-7)-10(-6) M) and cAMP (10(-6)-10(-4) M) stimulated (Ca2++Mg2+)-ATPase activity dose-dependent and their stimulatory effects were inhibited completely by 5 microM H-8, an inhibitor of cAMP-dependent protein kinase. PTH (10(-7) M) also caused 40% increase in 32P incorporation into the BLM and 5 microM H-8 inhibited this increase too. PTH (10(-7) M) was found to stimulate phosphorylation of a protein of Mr 9000 by cAMP dependent protein kinase and 5 microM H-8 was found to block this stimulation also. From these results, it is proposed that PTH stimulates (Ca2++Mg2+)-ATPase activity by enhancing its affinity for free Ca2+ via cAMP-dependent phosphorylation of a BLM protein of Mr 9000.
Itoh
K
K
Department of Medicine and Geriatrics, Osaka University Medical School, Japan.
Morimoto
S
S
Shiraishi
T
T
Taniguchi
K
K
Onishi
T
T
Kumahara
Y
Y
D000818:Animals; D017301:Ca(2+) Mg(2+)-ATPase / Q000378:metabolism*; D002118:Calcium / Q000494:pharmacology; D000252:Calcium-Transporting ATPases / Q000378:metabolism*; D002462:Cell Membrane / Q000201:enzymology; D000242:Cyclic AMP / Q000494:pharmacology*; D004285:Dogs; D007546:Isoquinolines / Q000494:pharmacology; D007668:Kidney / Q000187:drug effects / Q000201:enzymology*; D007700:Kinetics; D010281:Parathyroid Hormone / Q000494:pharmacology*; D010766:Phosphorylation; D047428:Protein Kinase Inhibitors; D011494:Protein Kinases / Q000378:metabolism*; D014268:Trifluoperazine / Q000494:pharmacology
D007546:Isoquinolines; D010281:Parathyroid Hormone; D047428:Protein Kinase Inhibitors; D014268:Trifluoperazine; C053177:N-(2-(methylamino)ethyl)-5-isoquinolinesulfonamide; D000242:Cyclic AMP; D011494:Protein Kinases; D017301:Ca(2+) Mg(2+)-ATPase; D000252:Calcium-Transporting ATPases; D002118:Calcium