Insulin increases glucose disposal into muscle. In addition, in vivo insulin elicits distinct nitric oxide synthase-dependent vascular responses to increase total skeletal muscle blood flow and to recruit muscle capillaries (by relaxing resistance and terminal arterioles, respectively). In the current study, we compared the temporal sequence of vascular and metabolic responses to a 30-min physiological infusion of insulin (3 mU · min-1 · kg-1, euglycemic clamp) or saline in rat skeletal muscle in vivo. We used contrast-enhanced ultrasound to continuously quantify microvascular volume. Insulin recruited microvasculature within 5-10 min (P < 0.05), and this preceded both activation of insulin-signaling pathways and increases in glucose disposal in muscle, as well as changes in total leg blood flow. Moreover, L-NAME (Nω-nitro-L-arginine-methyl ester), a specific inhibitor of nitric oxide synthase, blocked this early microvascular recruitment (P < 0.05) and at least partially inhibited early increases in muscle glucose uptake (P < 0.05). We conclude that insulin rapidly recruits skeletal muscle capillaries in vivo by a nitric oxide-dependent action, and the increase in capillary recruitment may contribute to the subsequent glucose uptake.

Item Type:	Refereed Article
Research Division:	Medical and Health Sciences
Research Group:	Clinical Sciences
Research Field:	Endocrinology
Objective Division:	Health
Objective Group:	Clinical Health (Organs, Diseases and Abnormal Conditions)
Objective Field:	Diabetes
Author:	Vincent, MA (Dr Michelle Keske)
Author:	Clark, MG (Professor Michael Clark)
Author:	Rattigan, S (Professor Stephen Rattigan)
ID Code:	31441
Year Published:	2004
Web of Science® Times Cited:	243
Deposited By:	Biochemistry
Deposited On:	2004-08-01
Last Modified:	2010-03-24
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