20 YEARS RESEARCH IN THE SECTION OF ENDOC RINOLOGY IN MARIENSEE - RECENT RESULTS IN RESEARCH OF HORMONAL AND MOLECULAR CONTROL OF GROWTH INTHE PIG

The article summarizes recent work from the Section of Endocrinology, Mariensee, regarding hormonal and molecular control of growth in the p ig. Special attention is paid to the regulation of growth hormone (GH) secretion In the fetal pig and the comparison of two different genoty pes, the Gottingen Miniature and the German Landrace pla. Plasma GH (a nd IGF-1) is enormously elevated in the fetal pig, apparently affectin g body composition. Our in vivo and in vitro studies indicate an ontog enetic increase in GH mRNA, a sex difference, an early responsiveness to GRF; pulsatile secretion of GH, immaturity of the opioid system aff ecting GH levels and postnatal maturation of inhibitory systems (somat ostatin and IGF-1) responsible for the dramatic postnatal decrease in plasma GH levels. Comparison of the German Landrace with the Gottingen Miniature pig indicates several important breed differences with resp ect to insulin levels, GH binding protein, plasma and in vitro GH resp onsiveness to GRF as well as in vitro responsiveness to somatostatin w ith ''paradoxical'' positive effects on GH dominating in the Gottingen Miniature pig. In vivo both breeds respond to a somatostatin agonist with an unexpected increase in plasma GH levels. These novel findings force to reconsider the role of somatostatin in the control of GH in t he pig and suggest that immunoneutralisation of somatostatin is not a practical tool for augmentation of plasma GH levels and thus not appro priate for growth promotion in the pig.