Plasma levels of somatostatin following a test meal in dogs Initial atropine resistant vagally mediated decrease of somatostain levels and increase of gastrin and insulin levels

Abstract

Plasma levels of somatostatin like immunoreactivity (SLI), below referred to as somatostatin levels, were measured in peripheral plasma of conscious dogs. Basal somatostatin levels averaged 49±10 pM. Somatostatin as well as gastrin and insulin plasma levels were measured before and after feeding with and without prior atropinization. During the first 10 min after feeding somatostatin levels fell from 49±10 to 23±9 pM, whereas gastrin and insulin levels rose from 9±2 and 140±14 pM to 48±11 and 370±91 pM respectively. Atropine 0.01 or 0.1 mg/kg did not inhibit these responses. After the initial decrease, somatostatin levels rose again and peaked at around 60 min after feeding (110±24 pM). This secondary rise was completely abolished by atropine in both doses tried. Gastrin and insulin levels remained elevated throughout the experiments with and without atropine. It is suggested that gastrin release and HCI secretion are inhibited by a tonic outflow of gastric somatostatin during basal conditions. The process of feeding induces an atropine resistant, vagally mediated decrease in somatostatin release from the gastrointestinal tract and this decreased output of somatostatin facilitates initiation of meal-related endocrine and exocrine gastric secretions.