DISPLACEMENT OF INSULIN FROM BLOOD CAPILLARIES

Normal anaesthetized bull-dogs were perfused with constant amounts of 125I bovine insulin. During the control period, steady state arterio-venous gradients and lymph levels were achieved. Positive arterio-venous differences were observed across the hind limbs and the head. Lower levels of 125I-insulin were found in cervical and leg lymph than in corresponding venous plasma. The rapid intravascular injection of unlabelled insulin resulted in an almost immediate reversal of the arterio-venous gradients of 125I-insulin in the head and the hind limb. The injection of small amounts of glucose into the lower abdominal aorta induced a very rapid diminution of the arterio-venous gradient across the hind quarters; the effect was not mediated by the release of endogenous insulin. In both experiments, the lymph levels of 125I-insulin remained relatively constant. The data indicate that the vascular pole of the capillary endothelial cells can adsorb labelled insulin and either exchange it with unlabelled insulin or release it under the direct influence of glucose. © 1969 Springer-Verlag.