Ontogeny of somatostatin in the human gastro-intestinal tract, endocrine pancreas and hypothalamus

Abstract

The appearance, time and distribution of somatostatin in the pancreas, gastro-intestinal tract and hypothalamus were studied comparatively in human fetuses aged 6-32 wk, by immuno-cytochemistry and radioimmunoassay. Somatostatin was detected by both methods in all segments including the colon. The 1st cells were observed, and somatostatin was present in measurable amounts at 8 wk in pancreas, duodenum and intestine, while the peptide was detected at 12 wk in antrum and colon, at 14 wk in fundus, and at 16 wk in hypothalamus. Subsequently, the largest cell population was located in the pancreas, where peptide concentration and age were positively correlated (P < 0.01, correlation coefficient = 64). From 15-21 wk of age, the mean somatostatin concentration in pancreas (12.4 .+-. 1.84 ng/mg) was clearly higher than in hypothalamus (0.05 .+-. 0.02 ng/mg) or in any segment of the gut, where values ranged from 0.36 .+-. 0.06 (fundus) to 4.74 .+-. 0.83 ng/mg (duodenum). The early appearance time of somatostatin, and its specific distribution with preferential location in the pancreas, suggest that the peptide may play a major role for the development of the fetal digestive tract, and that it may be involved in the regulation of other endocrine secretions, especially in the pancreas.