68 ONTOGENETIC DEVELOPMENT OF THYROTROPIN-RELEASING H0R M0NE (TRH) IN HUMAN PANCREAS

Pancreas is the most relevant extrahypothalamic source of TRH. We previously reported that pancreatic TRH content in rats is higher at birth and declines after few weeks. In the present study the ontogenesis of pancreatic TRH in human fetuses and in infants has been evaluated. 12 fetuses of 15-36 w of gestation were obtained after pregnancy interruption; their pancreata and those of 2 infants died at 1 yr were taken within 8 hr. TRH was measured by a RIA in methanolic extracts of whole pancreas and the results were expressed as pg/mg of wet tissue weight. TRH was detectable at 15-21 w of gestation with values from 0.5 to 1.5 pg/mg; a progresive increase was observed with a maximal value of 6.4 pg/mg at 28 w, while a progressive reduction was observed up to the birth, when the mean value was 2.4 pg/mg; in infants of 1 yr the value was 1.5 pg/mg. Human pancreatic TRH had chromatographic, immuno-reactive and serum inactivation properties similar to synthetic TRH. The rise of pancreatic TRH content from 15 to 28 w was paral leled by a similar increase of pancreatic content of insulin. In conclusion, the TRH is present in human fetal pancreas and its ontogeny is characterized by a biphasic pattern.