AJP - Regulatory, Integrative and Comparative Physiology, Vol 270, Issue 2 450-R455, Copyright © 1996 by American Physiological Society
Effect of insulin on regional vascular resistances in conscious rats
E. Qadir and J. P. Porter
Department of Physiology, University of Louisville, Kentucky 40292, USA.
In the rat, but not in humans and other mammals, chronic administration of
insulin produces hypertension. The present aim was to determine the effect
of acute insulin infusion on regional vascular resistances and to determine
the neurogenic contribution to the response. Conscious rats were infused
with insulin (2 or 6 mU/min) before and after ganglionic blockade with
chlorisondamine (5 mg/kg). The low dose of insulin produced an increase in
arterial pressure and hindquarter vascular resistance; the high dose
produced a gradual decrease in arterial pressure and renal resistance.
After ganglionic blockade, the hindquarter vasoconstriction produced by the
low dose was abolished. The high dose of insulin produced both hindquarter
and renal vasodilation. Thus the low dose of insulin had a selective
neurogenic vasoconstrictor effect in rat skeletal muscle vascular beds.
With higher doses, direct vasodilatory effects in both skeletal muscle and
renal vascular beds appeared. This greater sensitivity of the
sympathoexcitatory effects of insulin in rats may explain the ability of
chronic insulin infusions to increase blood pressure in this species.
