Insulin transport across capillaries is rate limiting for insulin action in dogs.

Abstract

This study examined the relationship between transcapillary insulintransport and insulin action in vivo. During euglycemic clamps (n = 7) in normal conscious dogs we simultaneously measured plasma and thoracic duct lymph insulin and glucose utilization (Rd). Clamps consisted of an activation phase with constant insulin infusion (0.6 mU/kg per min) and a deactivation phase. 14CIInulin was infused as a passively transported control substance. While [14Cjinulin reached an equilibrium between plasma and lymph, steady-state (ss) plasma insulin was higher than lymph (P < 0.05) and the ratio of 3:2 was maintained during basal, activation, and deactivation phases: 182 vs. 121, 512 vs. 321, and 183 vs. 131 ,U/ml. In addition, it took longer for lymph insulin to reach ss than plasma insulin during activation and deactivation: 112 vs.