Effects of subbasal insulin infusion on resting and exercise-induced glucose turnover in depancreatized dogs

β-Adrenergic blockade suppressed lipolysis and normalized the exercise- induced increments in glucose uptake (Glc(U)) and metabolic clearance rate (MCR) in alloxan-diabetic dogs with residual insulin, but not in insulin- deprived depancreatized dogs even when combined with methylpalmoxirate (MP), which suppresses fatty acid oxidation. The effects of a minimal amount of insulin (as in the alloxan-diabetic dog), were studied in depancreatized, 24- h insulin-deprived dogs during rest and treadmill exercise (6 km/h, 10% slope) using a 1/4 basal insulin infusion (50 μU · kg^-1 · min^-1, insulin, n = 6) alone, or with MP (20 mg · kg^-1 · day orally, 2.5 days, MP + insulin, n = 6). At rest, insulin decreased circulating fatty acids (31%) and Glc (13%) and increased Glc(U) and MCR (86 and 72%). Glc production was unaffected. MP plus insulin markedly suppressed hepatic fatty acid oxidation, decreased Glc (44%) and Glc production (50%), and markedly increased MCR (128%). The exercise-induced increments in MCR were markedly improved only by MP plus insulin but were still lower than in the propranolol-treated alloxan-diabetic dogs. Plasma Glc inversely correlated with the exercise-induced increase in MCR (r = -0.86). We conclude that 1) acute infusion of subbasal insulin improved Glc(U) in depancreatized dogs at rest but not during exercise; 2) inhibition of fatty acid oxidation combined with subbasal insulin improved the exercise-induced increase in MCR; and 3) the difference in Glc(U) and MCR between the MP plus insulin-treated depancreatized dogs and the β-blockade-treated alloxan-diabetic dogs suggests a difference between acute and chronic effects of insulin.