Inhibition of glucagon secretion by crude liver extract in conscious dogs

The feedback regulation between the endocrine gland and its target organ is an expected biological relationship. However, such a phenomenon is not documented between the endocrine pancreas and its major target organ, the liver. Several studies have documented a relationship between hepatic glycogen content and fasting plasma glucagon suggesting that liver may be a modulator of the pancreatic alpha cell function. To further examine this hypothesis, this study determined plasma glucagon, insulin and glucose after an overnight fast and again at frequent intervals up to 60 minutes after an intravenous administration of either crude liver extract or normal saline, 2 ml in 6 conscious dogs. Plasma glucagon and glucose declined significantly following administration of liver extract (p < 0.01), with no alteration in plasma insulin. However, normal saline administration failed to induce changes in any of the parameters studied. Furthermore, integrated responses were significantly larger for glucagon and glucose (p < 0.01), but not for insulin during infusion of the liver extract when compared with normal saline study. Therefore, this study suggests that hepatic tissue may synthesize and secrete a putative factor capable of inhibiting glucagon secretion by the pancreatic alpha cells.