DEVELOPMENT OF GONADOTROPHS AND THYROTROPHS IN THE FEMALE FETAL SHEEPPITUITARY - IMMUNOCYTOCHEMICAL LOCALIZATION STUDIES

In order to investigate the ontogenesis of cell types in the pituitary gland, anterior pituitaries were collected from female foetal sheep a t days 70, 100 and 130 of gestation (term = 145 days). Cells containin g the common alpha-subunit and the specific beta-subunits of luteinizi ng hormone (LH), follicle-stimulating hormone (FSH) and thyroid-stimul ating hormone (TSH) were immunolocalized using the avidin-biotin immun operoxidase technique. LHbeta-containing cells were first detected in the foetal pituitary by day 70 of gestation. The number and intensity of staining of these LHbeta cells increased by day 100 but had decline d again by day 130. Immunopositive alpha-subunit and FSHbeta-cells app eared by day 100 of gestation and had further increased in number and staining intensity by day 130. Cells containing TSHbeta were present a t day 70 and progressively increased in abundance and intensity throug h gestation. These data indicate that the development of LH- and FSH-c ontaining cells in the female foetal sheep pituitary is differentially regulated during foetal life, and that in the sheep free alpha-subuni t is not produced in significant amounts before the specific beta-subu nits.