ONTOGENY OF GROWTH-HORMONE AND LH-BETA-SUBUNIT, FSH-BETA-SUBUNIT AND ALPHA-SUBUNIT MESSENGER-RNA LEVELS IN THE PORCINE FETAL AND NEONATAL ANTERIOR-PITUITARY

The mechanism underlying the ontogenetic increase in plasma growth hor mone (GH), luteinizing hormone (LH) and follicle stimulating hormone ( FSH) concentration during fetal life in mammalian species and the pren atal sex difference in these hormones in some species is not fully und erstood, To this end anterior pituitaries were collected from German L andrace fetuses and piglets at day (d) 50, 65, 80, 95, 110 pc and d 6 pp and pituitary GH, LH beta, FSH beta and alpha-subunit mRNA levels w ere determined by measuring Northern blot hybridization signals. GH mR NA was detected in both sexes as early as d 50 pc, The mRNA level mark edly increased with age in both sexes (males>females, P less than or e qual to 0.05) reaching its maximum at d 95/110 pc, LH beta mRNA signal s were first detected at d 50 pc in females and at d 65 pc in males in creasing thereafter to a maximum at d 6 pp in both sexes (P less than or equal to 0.05). In males the augmentation in LH beta mRNA was delay ed compared to females (P less than or equal to 0.01). Before d 80 pc no FSH beta mRNA hybridization signals were apparent. Thereafter the m RNA level continuously increased with age (P less than or equal to 0.0 1) in both sexes reaching its maximum at d 6 pp. The FSH beta mRNA lev el in females was always higher than in males (P less than or equal to 0.01). As early as d 50 pc the alpha-subunit mRNA level was high in b oth sexes and further increased without sex difference to d 6 pp (P le ss than or equal to 0.05). In conclusion, the mRNA levels of GH, LH be ta and FSH beta are age and sex dependent during fetal development, We suggest that the fetal increase in plasma GH concentration can be acc ounted for by changes in GH mRNA levels, while the dramatic perinatal decrease in plasma GH concentration seems to be primarily controlled a t the posttranslational and/or secretion level, The fetal sex differen ce and the increase in plasma LH and FSH concentrations seems to be pr imarily dependent on the cellular concentration of the gonadotropin be ta-subunit mRNAs and/or number of gonadotrophs.