Role of glucose and insulin loads to the exercising limb in increasing glucose uptake and metabolism.

To assess the contributions of glucose load to the working hindlimb and local contraction-related events (changes related to the microvasculature and/or intrinsic muscle metabolic properties) to the exercise-induced increases in muscle glucose uptake and metabolism in vivo, dogs were studied with somatostatin infused to suppress insulin release, and glucose and insulin were replaced 1) during rest and treadmill exercise at rates that recreate limb glucose and insulin loads evident during exercise (n = 5), 2) at rest to selectively normalize the limb glucose load to rates present during exercise while retaining basal limb insulin loads (GL, n = 5), or 3) at rest to normalize both the limb glucose and insulin loads to those present during exercise (IGL, n = 5). Limb arteriovenous difference and isotopic ([U-14C]glucose) techniques were used to quantify muscle glucose uptake and metabolism. Limb glucose load rose from 819 +/- 141 mumol/min in the basal state to 1,568 +/- 190 mumol/min with exercise. Limb glucose loads were 1,423 +/- 88 and 1,502 +/- 165 mumol/min in GL and IGL. The limb insulin load rose from basal rates of 12.9 +/- 2.3 to 22.9 +/- 5.9 nmol/min during exercise. Limb insulin loads were similar to basal loads in GL (8.8 +/- 1.9 nmol/min) and exercise in IGL (28.2 +/- 5.5 nmol/min).(ABSTRACT TRUNCATED AT 250 WORDS)