Insulin Dependence of the Actions of Growth Hormone and Somatostatin on Splanchnic Biogenic Amines of the Dog

Summary

It is known from studies previously conducted in this laboratory that an iv injection of ovine growth hormone (GH, 100 μg/kg BW) or an equimolar amount of somatostatin (SRIF, 7.5 μg/kg BW), given to normal conscious dogs into a saphenous vein, leads to a significant increase in hepatic portal plasma serotonin and a simultaneous decrease in the concentrations of dopamine, norepinephrine and epinephrine. The changes take place within 12 minutes after the injection and are observed only in the portal circulation. The purpose of the present experiment was to investigate whether or not similar results could be obtained in diabetic animals. Mongrel dogs were rendered diabetic by surgical pancreatectomy and fitted with an indwelling hepatic portal catheter. Radioenzymatic methods were employed for quantitative measurements of plasma free serotonin and catecholamines. No response was noted when the same type of experiments as those conducted in normal dogs were now carried out in trained, fully conscious totally pancreatectomized dogs deprived of exogenous insulin supply. When the same animals were given an injection into a peripheral vein of 50 mU/kg BW regular crystalline insulin (a small dose that affected neither plasma glucose nor biogenic amine levels) 10 minutes prior to the administration of the other hormones, the usual response to both GH and SRIF was restored, i.e. the data were comparable to those of normal dogs. It is concluded that the GH/SRIF effect on gut biogenic amines is insulin dependent.

Key-Words

Serotonin - Catecholamines - Hepatic Portal Vein - Growth Hormone - Somatostatin - Insulin - Pancreatectomized Dogs