Cellular mechanisms of vasopressin and endothelin to mobilize [Mg2+]i in vascular smooth muscle cells.
The present study was undertaken to examine the effects of arginine vasopressin (AVP) and endothelin-1 (ET-1) on cytosolic free Mg2+ ([Mg2+]i) in cultured rat vascular smooth muscle cells (VSMC). [Mg2+]i was measured using the fluorescence indicator dye mag-fura-2. AVP and ET-1 at a concentration of 1 x 10(-9) M or higher induced the mobilization of [Mg2+]i and cytosolic free Ca2+ ([Ca2+]i) in a dose-dependent manner in rat VSMC. Atrial natriuretic peptide and sodium nitroprusside producing cellular guanosine 3',5'-cyclic monophosphate did not affect [Mg2+]i and [Ca2+]i. A diterpene activator of adenylate cyclase, forskolin, also did not alter [Mg2+]i and [Ca2+]i. The removal of extracellular Mg2+ enhanced the AVP-mobilized [Ca2+]i and did not change the AVP-mobilized [Mg2+]i. The Ca(2+)-free and nominally Mg2+/Ca(2+)-free states decreased the AVP-mobilized [Mg2+]i and [Ca2+]i. The Na(+)-free state enhanced the sustained, but not peak, level of the AVP-mobilized [Mg2+]i. These results indicate that AVP and ET-1 mobilize [Mg2+]i mediated through their intracellular second messenger [Ca2+]i and independent of extracellular Mg2+. Also, an increase in [Mg2+]i is indicated to stimulate the Na(+)-Mg2+ exchange to increase cellular Mg2+ efflux.
Okada
K
K
Department of Medicine, Jichi Medical School, Tochigi, Japan.
Ishikawa
S
S
Saito
T
T
D000818:Animals; D001127:Arginine Vasopressin / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D016232:Endothelins / Q000494:pharmacology*; D005110:Extracellular Space / Q000378:metabolism; D016257:Fura-2; D007474:Ion Exchange; D008274:Magnesium / Q000378:metabolism*; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000378:metabolism*; D009994:Osmolar Concentration; D051381:Rats; D012964:Sodium / Q000378:metabolism
D016232:Endothelins; D001127:Arginine Vasopressin; D012964:Sodium; D008274:Magnesium; D002118:Calcium; D016257:Fura-2