THE DIFFERENTIATION OF ENTERO-ENDOCRINE CELLS OF PRENATAL AND POSTNATAL RATS - LIGHT AND ELECTRON-MICROSCOPY AND IMMUNOCYTOCHEMISTRY

The differentiation of cholecystokinin/gastrin (CCK/GA)-, glucagon (GL U)- and somatostatin (SOM)-positive cells in the pre- and postnatal ra t duodenum was investigated with a special emphasis on the relationshi p to that of the fibromuscular intestinal wall by light and electron m icroscopy and immunocytochemistry. Between prenatal days 16 and 21, co ntacts of mesenchymal cells with the epithelium are frequent, and the differentiation of the entero-endocrine cells which occasionally displ ay a secretory function becomes advanced in close proximity to an exte nsive capillary network in the underlying connective tissue. CCK/GA-po sitive cells can be detected by immunocytochemistry in the intestinal epithelium at prenatal day 18. Other types of entero-endocrine cells a re not detected until prenatal day 19. Quantitative analysis demonstra tes that the volume density of CCK/GA-positive cells per 100 mu m(2) c ytoplasmic area increases sharply at postnatal day 5 relative to earli er stages. This may be mainly due to suckling of the neonatal rat.