THE ONTOGENESIS OF SOMATOSTATIN IN THE FETAL RAT AND SHEEP PANCREAS

Abstract

The localization of somatostatin (GIF) in pancreatic D cells and in the gastrointestinal tract led to the concept that SRIF may have a physiologic role at these sites as well as in the CNS. Its role in the fetus is not known. Previously we demonstrated GIF in the human fetal hypothalamus and cerebral cortex. The present study examines the ontogeny of GIF In rat and sheep fetal pancreas using a homologous radioimmunoassay with tyrosyl 11-GIF as label and standard, with a sensitivity of 5 pg cyclic GIF. In the rat, GIF is detected at 14 days gestation in pooled extracted pancreases at .0016 ng/pancreas. GIF increases proportional to DNA until day 19, with a subsequent rapid rise to 3.8 ng/pancreas (72 pg/μg DNA) at term. Two days postnatally GIF Increases to 8.3 ng/pancreas (135 pg/μg DNA). In the adult rat 71.3 ng GIF/pancreas is detected (54 pg/μg DNA). In the fetal sheep, GIF is present by 58 days at 1.6 ng/pancreas, rises to 5.3 ng at 65 days and to 1900 ng/pancreas at term. The content in the adult sheep is 7000 ng GIF/pancreas. GIF is present by mid-gestation in the fetal rat and sheep pancreas with a sharp 1000-fold increase by term. The biphasic developmental pattern of somatostatin in the fetus is similar to that of insulin but differs from that for glucagon.