Vasodilator effect of insulin on the microcirculation of the rat cremaster muscle.
We recently showed that, in conscious rats, acute infusions of insulin (10-15 fold increase in plasma insulin) produced decreases in hindquarter vascular resistance, but only if, changes in sympathetic outflow were prevented with a ganglionic blocker. The aim of the present investigation was to determine if similar effects of insulin could be observed in a preparation that allowed direct visualization of striated muscle (cremaster) microvessels. Initial studies with topical application of insulin showed that third-order arterioles (A3), but not first- or second-order arterioles vasodilated in response to 800 microU/ml and 8 mU/ml of insulin. Systemic (euglycemic) infusion of insulin (6 mU/ml, but not 2 mU/ml) also increased A3 arteriole diameter in animals treated with a ganglionic blocker, but not in control rats. These data show that insulin can have a direct vasodilator effect on striated muscle microvessels if concomitant increases in sympathetic outflow are absent. However, the response was only present with supraphysiological doses of the hormone.
Porter
J P
JP
Department of Physiology, School of Medicine, University of Louisville, KY 40292, USA.
Joshua
I G
IG
Kabithe
D
D
Bokil
H S
HS
D000287:Administration, Topical; D000818:Animals; D001160:Arterioles / Q000187:drug effects* / Q000502:physiology; D001794:Blood Pressure / Q000187:drug effects; D002714:Chlorisondamine / Q000008:administration & dosage / Q000494:pharmacology; D005730:Ganglionic Blockers / Q000008:administration & dosage / Q000494:pharmacology; D006339:Heart Rate / Q000187:drug effects; D007262:Infusions, Intravenous; D007328:Insulin / Q000008:administration & dosage / Q000494:pharmacology*; D008297:Male; D018482:Muscle, Skeletal / Q000098:blood supply*; D051381:Rats; D017207:Rats, Sprague-Dawley; D014665:Vasodilator Agents / Q000008:administration & dosage / Q000494:pharmacology*
D005730:Ganglionic Blockers; D007328:Insulin; D014665:Vasodilator Agents; D002714:Chlorisondamine