Plasma gonadotrophins (LH and FSH) were radio-immunoassayed before and after injection of 0.1 mg/m2 of synthetic luteinizing hormone\x=req-\ releasing hormone (LH-RH) in infants 1 to 12 months old, prepubertal children aged more than 12 months, and pubertal subjects of both sexes. The pubertal changes of gonadotrophins include a highly significant increase of LH pituitary mobilizable reserve in both sexes, while the FSH reserve shows a significant decrease in females and no significant variation in males. From the first year of life up to childhood, the basal blood levels of FSH and LH decrease significantly in girls but do not vary in boys, while the FSH reserve decreases significantly in girls and increases significantly in boys, the LH reserve showing a non-significant decrease in both sexes. In the first year of life, girls show a very significantly higher FSH secretion and reserve than boys, while boys have a significantly higher LH reserve than girls. After the end of the first year up to the onset of puberty, the FSH reserve remains significantly higher in girls than in boys. The interpretation of these facts is discussed.Radio-immunoassay of gonadotrophins (follicle-stimulating hormone (FSH) and luteinizing hormone (LH)) after the injection of luteinizing hormonereleasing hormone (LH-RH) evaluates the pituitary gonadotrophic reserve in
Teratocarcinoma cells in culture offer an in vitro system for studying certain aspects of embryonic differentiation. To gain some insight into regulatory systems that might be operative during early development, we have characterized the alterations that occur in the hormonal responsiveness of the F9 embryonal carcinoma cell membrane adenylate cyclase with differentiation. Adenylate cyclase of F9 cells is stimulated in the presence of 10 GTP by calcitonin, prostaglandin E ,, ( -) isoproterenol, and epinephrine, while parathyroid hormone is only slightly effective. Of these active hormones, calcitonin is the most potent stimulator of cyclic AMP production. Exposure of F9 cells to retinoic acid induces differentiation to parietal endodermal cells. Basal, GTP-, and fluoride-stimulated adenylate cyclase activities show a progressive increase with the retinoic acid-induced change to the endodermal phenotype. Differentiation to the endodermal cell type markedly alters the adenylate cyclase response to calcitonin and parathyroid hormone; the cyclase of endodermal cells exhibits a low response to calcitonin while parathyroid hormone dramatically enhances cyclic AMP formation.Treatment of the retinoic acid-generated endodermal cells with dibutyryl cyclic AMP converts these cells to a type exhibiting neural-like morphology. The adenylate cyclase system of these cells is only stimulated by parathyroid hormone, prostaglandin El, isoproterenol, and epinephrine. Calcitonin responsiveness has been lost in these cells. These variations in calcitonin and parathyroid hormone responsiveness suggest a possible regulatory role for these hormones during embryonic development. Further more, the results indicate that changes in adenylate cyclase hormonal responsiveness might serve as useful markers during early stages of differentiation.
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