Non-insulin-mediated glucose uptake predominates in postabsorptive dogs

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Abstract
Overall glucose uptake represents the sum of insulin-mediated glucose uptake (IMGU) and non-insulin-mediated glucose uptake (NIMGU). In this study, we compared the rate of NIMGU in conscious and anesthetized dogs. Rates of glucose disposal were compared in the basal state and during severe insulinopenia after endogenous insulin suppression by high-dose somatostatin (SRIF) infusion. Steady-state NIMGU rates were calculated 2 h after commencing SRIF infusion. Three groups of studies were performed: 1) SRIF in conscious dogs; 2) SRIF in anesthetized dogs; and 3) SRIF plus glucagon, also in anesthetized dogs. In all three groups, serum insulin levels were reduced to below assay sensitivity after SRIF infusion. The basal metabolic clearance rate of glucose (MCRg) for each group was 3.8 +/- 0.4, 3.6 +/- 0.3, and 3.6 +/- 0.3 ml X kg-1 X min-1, respectively (P = NS, all groups). Steady-state NIMGU rates were 2.4 +/- 0.2 (conscious), 2.5 +/- 0.1 (anesthetized, SRIF only), and 2.4 +/- 0.1 ml/kg/min (anesthetized, SRIF plus glucagon). Thus, absolute rates of NIMGU expressed as MCRg in conscious and anesthetized animals do not differ and in the three groups studied comprise approximately the same proportion of the basal glucose uptake (approximately 64, approximately 69, and approximately 66%, respectively). We conclude that approximately 66% of basal postabsorptive glucose uptake occurs via NIMGU mechanisms and that this pathway is unaffected by anesthesia and surgery.