Effect of glucose and insulin infusion on the myocardial extraction of a radioiodinated methyl-substituted fatty acid

We investigated the one-way. AV extraction of 14-iodophenyl-tetradecanoic acid (BMTDA) in the canine heart under fasting conditions and during infusion of glucose plus insulin in eight anesthetized greyhound dogs. Myocardial extraction measurements were made with dual tracer approach, using Tc-99m albumin as reference tracer. Prior to, and during, infusion of 10% glucose and 25 units of regular insulin, heart rate, blood pressure, plasma glucose, insulin and free fatty acid levels were measured. Myocardial blood flow was determined using Sn-113 and Ru-103 radioactive microspheres. The mean extraction fraction of BMTDA was 0.38±SEM 0.06 at baseline and increased to 0.44±0.06 during hyperglycemia plus insulin (P<0.025). Plasma glucose and insulin were higher during the infusion (P<0.01) while plasma free fatty acids significantly declined (P<0.01). There were no changes in hemodynamics or myocardial blood flow during the infusion. We conclude that glucose and insulin infusion result in increased firstpass extraction fraction of radioiodinated BMTDA unaccompanied by changes in coronary flow or hemodynamics, implying an insulin-mediated augmented transport of BMTDA.