Effect of Pancreatectomy on Glucose Tolerance and Extracellular Fluid Insulin in the Dog

Abstract

An intravenous glucose tolerance test (IVGTT No. 1) was performed in anesthetized dogs after dissection of the pancreas but prior to its removal. The test was repeated forty minutes (IVGTT No. 2) and three hours and forty minutes (IVGTT No. 3) after the pancreatectomy was completed. Glucose, immunoreactive insulin (IRI), and insulin-like activity (ILA) were measured in serum and in thoracic duct lymph. During IVGTT No. 1, serum IRI concentration rose sharply and then decreased while lymph IRI increased more slowly and reached a plateau at twice the fasting level. Net glucose disappearance rate (K) was 1.7 per cent per minute. Forty minutes after pancreatectomy, at the initiation of IVGTT No. 2, lymph IRI had decreased to 50 per cent of the fasting level, but blood glucose concentrations were still within the normal range. At this point, following glucose injection, no increase in serum or lymph IRI was observed and glucose tolerance was subnormal: K = 0.5 per cent per minute. Further lowering of lymph IRI and hyperglycemia were noted three hours and forty minutes after pancreatectomy. IVGTT No. 3 showed further deterioration of carbohydrate tolerance: K < 0.5 per cent per minute. Thus, progressive reduction in the rate of glucose assimilation was observed pari passu with reduction in the plateau level of interstitial IRI. It is suggested that this moiety is probably the major determinant of net glucose disappearance rate. Endogenous serum IRI rapidly equilibrated with interstitial fluid IRI. On the other hand, changes in serum “nonsuppressible” insulin-like activity (NSILA) were not reflected in lymph NSILA levels, thus suggesting that this moiety does not play a major role in the assimilation of a glucose load.