title: Insulin increases vascular smooth muscle recovery from intracellular calcium loads.
abstract: Insulin has previously been shown to attenuate vasoconstrictor responses to pressor agonists and accelerate vascular smooth muscle relaxation and vascular smooth muscle Ca2+ efflux. To further determine the role of insulin in regulating vascular smooth muscle Ca2+, quiescent A7r5 cultured vascular smooth muscle cells and human vascular smooth muscle cells were incubated with or without 10(-7) or 10(-8) M insulin for 1 hour and then loaded with fura 2-AM; intracellular Ca2+ responses to and rates of recovery from angiotensin II (200 nM) and arginine vasopressin (AVP) (10 microM) were studied fluorometrically in stirred suspension. Insulin (10(-7) M) caused an increase in the peak intracellular Ca2+ response to angiotensin II (peak/baseline x 100 = 469 +/- 96 versus 288 +/- 74, P < .05) and a decrease in the peak Ca2+ response to vasopressin (288 +/- 50 versus 389 +/- 33, P < .025). However, insulin also caused a marked increase in the rate of intracellular Ca2+ recovery to baseline after stimulation with both angiotensin II (77.3 +/- 13.8 versus 30.6 +/- 6 nM/min, P < .03) and vasopressin (P < .05), such that the cumulative exposure to elevated intracellular Ca2+ after stimulation with either agonist (ie, area under the intracellular Ca2+ curve) was reduced with insulin treatment. Insulin (10(-8)) caused small but still significant effects on all parameters in the A7r5 cells. Insulin also caused comparable effects on Ca2+ recovery in the human cells but was without significant effect on peak Ca2+ responses to AVP.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Nutrition, University of Tennessee, Knoxville 37996-1900.
authors.forename: Y C
authors.initials: YC
authors.lastname: Kim
authors.forename: M B
authors.initials: MB
authors.lastname: Zemel
mesh_terms: D000804:Angiotensin II / Q000494:pharmacology; D000818:Animals; D001127:Arginine Vasopressin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002460:Cell Line; D006801:Humans; D007328:Insulin / Q000494:pharmacology / Q000502:physiology*; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D012044:Regression Analysis; D013997:Time Factors
chemical_list: D007328:Insulin; D000804:Angiotensin II; D001127:Arginine Vasopressin; D002118:Calcium