Effects of ouabain on cytosolic calcium in lymphocytes, platelets and adrenomedullary cells.
It has been suggested that a circulating inhibitor of Na/K ATPase can stimulate natriuresis and cause vasoconstriction in essential hypertension by stimulating transmembrane Na/Ca exchange to produce increased cytosolic concentrations of ionized calcium ([Ca++]i) in renal tubular and arteriolar smooth muscle cells. If this inhibitor affected [Ca++]i in all cell types, then clinical assays for its presence could be applied to easily accessible cells such as blood cells or platelets, and the inhibitor could exert a hormonal action on Ca++-dependent adrenomedullary secretion of catecholamines. We used the Quin 2 technique for measuring [Ca++]i in lymphocytes, platelets and adrenomedullary cells in response to ouabain. Inhibition of Na/K ATPase by ouabain (10(-7) to 10(-3) mol/l enhanced transient [Ca++]i responses during Ca repletion but had no effect on steady-state [Ca++]i in any of the cell lines. Although it is possible that a Na/Ca exchange mechanism may exaggerate transient increases in [Ca++]i during Na/K ATPase inhibition, other mechanisms appear to buffer these acute perturbations of [Ca++]i in lymphocytes, platelets and adrenomedullary cells.
Hypertension-Endocrine Branch, National Heart, Lung and Blood Institute, Bethesda, Maryland 20892.
R
R
Zimlichman
D S
DS
Goldstein
S
S
Zimlichman
H R
HR
Keister
D000313:Adrenal Medulla / Q000166:cytology / Q000187:drug effects*; D000818:Animals; D001792:Blood Platelets / Q000187:drug effects*; D002118:Calcium / Q000032:analysis*; D002417:Cattle; D002478:Cells, Cultured; D003600:Cytosol / Q000032:analysis* / Q000187:drug effects; D006801:Humans; D008214:Lymphocytes / Q000187:drug effects*; D010042:Ouabain / Q000494:pharmacology*
D010042:Ouabain; D002118:Calcium