ISSN:
1432-0428
Keywords:
Keywords Insulin
;
nitric oxide
;
constitutive nitric oxide synthase
;
vascular smooth muscle
;
adenosine 3′ : 5′-cyclic monophosphate
;
guanosine 3′ : 5′-cyclic monophosphate.
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Abstract Aims/hypothesis. Insulin incubation of human vascular smooth muscle cells (hVSMC) for 120 min increases both guanosine 3′ : 5′-cyclic monophosphate (cGMP) and adenosine 3′ : 5′-cyclic monophosphate (cAMP) and these effects are blocked by inhibiting nitric oxide synthase (NOS). These data suggest that insulin activates a constitutive Ca2+-dependent NOS (cNOS), not described at yet in hVSMC. To test this hypothesis, we evaluated in hVSMC: i) the kinetics of the insulin-induced enhancement of the two cyclic nucleotides; ii) the ability of nitric oxide (NO) to increase both cyclic nucleotides; iii) NO involvement in the short-term influence of insulin on both cyclic nucleotides; iv) the ability of insulin to increase NO production in a few minutes; v) the presence of a cNOS activity; vi) the expression of mRNA for cNOS. Methods. In hVSMC incubated with insulin, NO donors and the Ca2+ ionophore ionomycin, we measured cAMP and cGMP (RIA); in hVSMC incubated with insulin and ionomycin we measured NO, evaluated as l-(3H)-citrulline production from l-(3H)-arginine; by northern blot hybridization, we measured the expression of cNOS mRNA. Results. i) By incubating hVSMC with 2 nmol/l insulin for 0–240 min, we observed an increase of both cGMP and cAMP (ANOVA: p = 0.0001). Cyclic GMP rose from 0.74 ± 0.01 to 2.62 ± 0.10 pmol/106 cells at 30 min (p = 0.0001); cAMP rose from 0.9 ± 0.09 to 11.65 ± 0.74 pmol/106 cells at 15 min (p = 0.0001). ii) Sodium nitroprusside (100 μmol/l) and glyceryltrinitrate (100 μmol/l) increased both cGMP and cAMP (p = 0.0001). iii) The effects of insulin on cyclic nucleotides were blocked by NOS inhibition. iv) An increase of NO was observed by incubating hVSMC for 5 min with 2 nmol/l insulin (p = 0.0001). v) Ionomycin (1 μmol/l) enhanced NO production (p = 0.0001) and increased both cyclic nucleotides (p = 0.0001). vi) hVSMC expressed mRNA of cNOS. Conclusion/interpretation. Human VSMC express cNOS, which is rapidly activated by insulin with a consequent increase of both cGMP and cAMP, suggesting that insulin-induced vasodilation in vivo is not entirely endothelium-mediated. [Diabetologia (1999) 42: 831–839]
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/s001250051234
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