Immunocytological Determination of Gonadotropic and Thyrotropic Cells in Fetal Rat Anterior Pituitary during Normal Development and under Experimental Conditions

Abstract

The appearance and relative distribution of immunoreactive gonadotropic and thyrotropic cells of the anterior pituitary of normal rat fetuses were studied by immunocytology with anti-rat luteinizing hormone serum, anti-porcine luteinizing hormone β serum, anti-bovine thyrotropic hormone serum after saturation with bovine luteinizing hormone. The thyrotropic cells appeared at 17 days of gestation. They were preferentially localized in the dorsal part of the anterior lobe. The gonadotropic cells localized in the ventral part of the same lobe, appeared 1 day later. The number of immunoreactive cells of the two populations increased until the end of gestation. In the pituitaries of 21-day-old rat fetuses encephalectomized at 16 days of gestation, the same number of gonadotropic and thyrotropic cells was observed as in control fetuses at the same age. Gonadotropic cells were also observed in rat adenohypophysial primordia explanted at 14 days of gestation and maintained in organ culture for 7 days. Thyrotropic cells were only stained when the primordia were explanted at 15 days of gestation and cultured for 6 days. No immunoreactive gonadotropic or thyrotropic cells were detected when explantation was performed before 14 days of gestation. These results clarify the problem of the role of hypothalamus on the differentiation of these two cell types.

Influence of Gonadoliberin on the Differentiation of Rat Gonadotrophs: An in vivo and in vitro Study

“…The method for organ culture was described elsewhere [3][4][5]. The culture media were made up starting from Parker's 199 with Hank's salt.…”

“…These results suggest that GnRH can stimulate the differentiation of gonadotrophs in early fetal life in synergy with insulin. This is supported by the intracellular presence of GnRH which is most likely of fetal origin, the possibility of the existence of a placental GnRH-like substance being not completely excluded.Several studies have presented evidence suggesting that the differentiation of gonadotrophs in the rat takes place independent of fetal hypothalamic gonadotropin-releasing activities [5,13,14]. The available results of in vitro experi ments are variable and unsatisfactory because of the use of uncontrolled serum in the culture medium [5,14,30] or the use of synthetic medium deprived of hormones and growth factors [22].…”

“…The available results of in vitro experi ments are variable and unsatisfactory because of the use of uncontrolled serum in the culture medium [5,14,30] or the use of synthetic medium deprived of hormones and growth factors [22]. However, in a previous report we showed that insulin and transferrin added to the culture medium could stimulate the spontaneous differentiation of gonadotrophs in adenohypophysial primordia maintained in organ culture [4], However, we showed that other stimulating factors were also involved since these cells were not able to differentiate Received: April 22, 1983 Accepted after revision: August 19, 1983 in these conditions of culture, when the explantation was performed at a very early stage.…”

Prenatal expression of interleukin 1β and interleukin 6 in the rat pituitary gland

“…and, finally, mammotrophic cells at day 19.5 p.c. [60][61][62][63][64]. Given the coincidence in time between cytokine expression detected by us and anterior pituitary functional differentiation during development, IL-1b and IL-6 might influence either the latter or hormonal release, as in adults.…”

Role of GnRH in the maturation of pituitary gonadotroph function

“…Although the hypophysial portal vasculature is not fully developed in the rat until 7 days of age (Glydon, 1957), electron microscope studies of the fetal median eminence show nerve terminals in close proximity to the perivascular spaces above the pituitary primordium as early as 16 days of gestation (Fink & Smith, 1971 (Chowdhury & Steinberger, 1976 (Begeot et al, 1981).…”