The effect of beta-endorphin on biogenic amines, insulin, and glucagon levels in the hepatic portal circulation of normal and pancreatectomized dogs

Abstract

The effect of peak concentrations of beta-endorphin on hepatic portal and peripheral levels of plasma catecholamines, free serotonin, glucose, insulin, and glucagon was studied in trained, conscious, normal adult dogs fitted with an indwelling portal catheter. An injection of synthetic human beta-endorphin (20 micrograms/kg BW) into a cephalic vein produced a significant rise in the portal concentration of dopamine, norepinephrine, and epinephrine. The rise was accompanied by a reduction of portal free serotonin levels. The changes were not seen in the peripheral circulation. No appreciable changes in plasma insulin, glucagon, and glucose concentrations were noticed either in the hepatic portal or in the peripheral circulation. The response of the biogenic amines to beta-endorphin was abolished by pretreatment with Naltrexone (1 mg/kg BW). A dose of somatostatin antiserum given before beta-endorphin did not alter the biogenic amine response to the opioid peptide. When beta-endorphin was administered to pancreatectomized dogs devoid of exogenous and endogenous insulin supply, the biogenic amine response remained virtually the same as in normal intact dogs. It is concluded that in the dog a pulse of beta-endorphin causes profound alterations of splanchnic biogenic amine concentrations that are independent of the ambient levels of insulin, somatostatin, and pancreatic glucagon.