Blood glucose control and insulin clearance in unrestrained diabetic dogs portally infused with a portable insulin delivery system.

Summary  Long term glucose control in pancreatectomised dogs has been obtained with portal insulin therapy. When compared to a previous similar study using peripheral infusions, 20% less exogenous insulin was required and peripheral fasting insulin levels were 30% lower. Animals (n = 5) were unrestrained, conscious and carried a programmable insulin pump for 163–224 days. In the post-absorptive state blood glucose was normal (87±5 mg/dl) as was plasma insulin (10±1 mU/l) with porcine insulin infused at a basal rate of 0.36±0.01 mU/kg/min. Following ingestion of a standard mixed meal the infusion rate was increased to 2.47±0.09 mU/kg/ min for 7 1/2 h resulting in post-prandial normalisation of blood glucose. Peripheral plasma insulin levels were twice normal during the post-prandial infusion, but only half those previously reported with peripheral infusions. Insulin clearance rates were 37 ml/kg/min in the basal state and rose significantly post-prandially. In the absence of extra meal-time insulin the clearance rate was unaffected by the resulting post-prandial hyperglycaemia and similar to values observed with insulin infused peripherally at 0.45±0.03 mU/kg/min. No significant increase in the post-prandial rate of insulin clearance relative to the fasting rate was observed with peripherally administered insulin. It was thus concluded that portal insulin replacement in pancreatectomised dogs could normalise both blood glucose and insulin in the fasting state, but post-prandial peripheral insulin levels remained elevated.