Increase in cytosolic calcium and phosphoinositide metabolism induced by angiotensin II and [Arg]vasopressin in vascular smooth muscle cells.
Effects of angiotensin II and [Arg]vasopressin on cytosolic free Ca2+ concentration ([Ca2+]i) and phosphoinositide metabolism were studied in cultured aortic smooth muscle cells obtained from Wistar-Kyoto rats and their spontaneously hypertensive substrain. [Ca2+]i was measured using the fluorescent Ca2+ indicator quin2. No clear differences in basal [Ca2+]i were detected between cells derived from the two strains. High concentrations of angiotensin II (greater than or equal to 10 nM) and [Arg]vasopressin (greater than or equal to 100 nM) elicited large and rapid increases in [Ca2+]i, followed by a rapid return to control values. Low concentrations of these peptides (less than or equal to 1.0 nM) elicited small and slow increases in [Ca2+]i that persisted for minutes. These responses were blocked by specific antagonists for each of these peptides. Only high concentrations of angiotensin II caused [Ca2+]i increases in "Ca2+-free" medium, which suggested that high concentrations of angiotensin II could release Ca2+ from intracellular pools. A high concentration of angiotensin II and [Arg]vasopressin elicited progressive accumulations of inositol phosphates. Only high concentrations of angiotensin II caused inositol phosphate accumulation in Ca2+-free medium. Maximal accumulation of inositol phosphate elicited by angiotensin II and [Arg]vasopressin was found to be additive. A desensitization to the effects of both peptides on Ca2+ mobilization occurred despite the continued accumulation of inositol phosphates. These observations indicated that angiotensin II and [Arg]vasopressin interacted with independent receptors, both of which are linked to phosphoinositide breakdown and Ca2+ mobilization.
Nabika
T
T
Velletri
P A
PA
Lovenberg
W
W
Beaven
M A
MA
D000255:Adenosine Triphosphate / Q000378:metabolism; D000634:Aminoquinolines; D000804:Angiotensin II / Q000494:pharmacology*; D000818:Animals; D001127:Arginine Vasopressin / Q000494:pharmacology*; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D002478:Cells, Cultured; D004533:Egtazic Acid / Q000494:pharmacology; D007295:Inositol Phosphates / Q000378:metabolism; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000378:metabolism*; D010716:Phosphatidylinositols / Q000378:metabolism*; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY
D000634:Aminoquinolines; D002121:Calcium Channel Blockers; D007295:Inositol Phosphates; D010716:Phosphatidylinositols; D000804:Angiotensin II; D001127:Arginine Vasopressin; D000001:Calcimycin; D004533:Egtazic Acid; D000255:Adenosine Triphosphate; C035739:Quin2; D002118:Calcium