Abstract. Galanin is a 29 amino acid peptide which has been found in intrapancreatic nerves. The effects of galanin, adrenergic and cholinergic blockade as well as somatostatin on the hormone release from the isolated perfused dog pancreas were studied. It was found that galanin dose-dependently inhibited insulin (P < 0.001) and somatostatin (P < 0.001) but not glucagon secretion at normal glucose levels. The lowest galanin concentration that caused a significant suppression of insulin and somatostatin secretion was 10−11and 10−10 mol/l, respectively. Similar effects were evident during stimulation with 2.5 mmol/l arginine. Galanin (10−9 mol/l) caused a more pronounced inhibition of insulin and somatostatin secretion at high (10 mmol/l) and normal (5 mmol/l) than at low glucose (1.3 mmol/l). In contrast, suppression of the glucagon secretion was only seen at low glucose (1.3 mmol/l). Perfusion of 10−6 mol/l of atropine, phentolamine and propranolol had no effect on the galanin-mediated (10−10 mol/l) inhibition of insulin and somatostatin secretion. Galanin (10−12–10−10 mol/l) and somatostatin (10−12 – 10−10 mol/l) were equipotent in inhibiting insulin secretion whereas only somatostatin exerted a suppression of the glucagon secretion at normal glucose. Thus, galanin exerts a differential effect on islet hormone secretion and may participate in the hormonal control of insulin, glucagon and somatostatin secretion.
K. Hermansen and A. M. Kappelgaard
Abstract. The 40 aminoacids residue of pancreatic growth hormone-releasing hormone stimulates the secretion of insulin, glucagon, an somatostatin from the pancreas. To determine whether this stimulation of islet hormone secretion is mediated via adrenergic or cholinergic receptor sites, we studied the effects of 30 nmol/l of the growth hormone-releasing hormone on the release of insulin, glucagon, and somatostatin in the presence of either α-adrenergic (phentolamine), β-adrenergic (propranolol) or cholinergic (atropine) blocking agents. The responses to the growth hormonereleasing hormone were not significantly modified by adrenergic or cholinergic blockers. The findings rule out an interaction with adrenergic and cholinergic receptors on islet cells. It is at present unknown whether the growth hormone-releasing hormone stimulates islet hormone secretion via an interaction with specific growth hormone-releasing hormone receptors or vasoactive intestinal peptide receptors.
K. Hermansen, A. Møller, C. K. Christensen, J. S. Christiansen, O. Schmitz, H. Ørskov, K. G. M. M. Alberti and C. E. Mogensen
Abstract. In addition to hyperglycaemia, derangement of metabolic and hormonal control may play an important role in the development of microvascular complications in diabetes. Little, however, is known about the impact of insulin pump treatment on metabolic and hormonal parameters. In a 6-month prospective randomized study in insulin-dependent diabetics we therefore investigated the effects of continuous subcutaneous insulin infusion by pump (10 patients) and conventional insulin treatment (10 patients) on the 24-h profiles of blood glucose, glycerol, lactate, 3-hydroxybutyrate, insulin, glucagon and growth hormone by measuring the respective concentrations every 2 h.
We found that average blood glucose levels and HbA1c were significantly lower in the group treated by continuous subcutaneous insulin infusion as compared with the group on conventional insulin treatment. Furthermore, we observed an improvement in diurnal levels of lactate and 3-hydroxybutyrate in the pumptreated group which was not seen in the conventionally treated group. A slight increment in alanine was seen in the group treated with insulin pump. Serum growth hormone, glycerol, plasma free insulin as well as the daily insulin supply were unchanged and identical in the two groups. It is noteworthy that in the pump group, the decrease in blood glucose and 3-hydroxybutyrate takes place concomitantly with a significant suppression of glucagon.