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Simultaneous monitoring of pancreatic and hepatic blood flows and serial analyses of blood glucose and immunoreactive insulin activity in arterial, portal, intestinal and hepatic venous blood were performed in anaesthetized laparotomized dogs. Based on these measurements, the rates of pancreatic insulin secretion, of hepatic insulin uptake and the hepatic glucose balance were computed. Under basal conditions pancreatic output was about 40% of the total hepatic insulin input. 30% of hepatic insulin inflow were actually taken up in the liver. During a primed i.v. glucose infusion (steady blood glucose concentration about 330 mg/100 ml) pancreatic and hepatic blood flows increase rapidly and the insulin secretion exhibits a biphasic pattern. The relative part of hepatic insulin inflow taken up in the liver remained unchanged. A non-primed i.v. glucose infusion provoked a slow increase of blood flow and a rapid but monophasic increase of insulin release. Under these conditions the relative hepatic insulin uptake was transiently increased. During both loads hepatic glucose balance switched from release to uptake. However the non-primed infusion was more effective. When pancreatic and hepatic blood flows were increased without any blood glucose alteration by an infusion of mannitol, insulin secretion did not change; hepatic uptake of insulin decreased, but hepatic glucose output was clearly reduced. A correlation between the rates of insulin secretion, of hepatic insulin inflow and of insulin uptake was observed under all conditions. However, the hepatic glucose balance was correlated to the inflow of insulin or glucose and to the hepatic insulin uptake under certain conditions in individual experiments only.

Suisynchron, a derivative of bisthio-urea commonly used for oestric synchronisation, was applied to nine female Alsatians over 21 days. All animals received intravenous glucose injections before ten, and 21 days from the beginning of treatment as well as 21, and 84 days after the end of treatment. The glucose-stimulated plasma insulin levels were significantly reduced during Suisynchron treatment and 21 days after the end of treatment. Both glucose tolerance and response of free fatty acids remained unaffected. This phenomenon might be attributable to a stimulated hepatic insulin degradation, to a biguanid-like effect on "peripheral" glucose turnover, or to an inhibited secretion of hormonal insulin antagonists of the anterior lobe of the pituitary gland. However, the long persistence of the Suisynchron action after interruption of treatment, could not be explained by any of these effects.