Localization of Luteinizing Hormone (LH) and Testosterone (T) or Dihydrotestosterone (DHT) in the Gonadotropic Cells of the Anterior Pituitary by using Ultracryomicrotomy and Immunocytochemistry

The action of gonadal steroids are mediated through the binding to specific intracellular receptors. Our recent studies have demonstrated that estrogen (E) treatment will increase the concentration of cytosolic androgen receptor (AR) in the anterior pituitary (AP) gland perhaps reflecting in increased sensitivity of this tissue circulating androgen. However, chronic E treatment also increases AP weight and cell number. Consequently, the following studies were performed to determine the relationship between increases in AP cytosolic AR and increases in AP weight following chronic E treatment. Gonadectomized male and female Fischer 344 (F344) rats were implanted with a 5-mm Silastic capsule of 17β-estradiol. Control animals were sham implanted. Animals were sacrificed at 1 3, 7 and 21 days after the commencement of E treatment and AP glands were weighed and processed for cytosolic AR and nuclear estrogen receptor (ER) content. AR and ER were determined by in vitro binding assays using ³H-dihydrotestosterone and ³H-estradiol, respectively. AP weight increased significantly by 3 days of E treatment in females and by 7 days in males (p < 0.05). However, AP weight of E-treated males was significantly less than females throughout (p < 0.05). Significant increases in AP cytosolic AR content (fmol bound/gland) were detected within 1 day of E treatment to female rats but not until 7 days in male rats. AP cytosolic AR content peaked at 7 days of E treatment in females and 21 days in males. AP cytosolic AR concentration (expressed as per milligram cytosol protein) peaked 3 days after E at which time there were significant E effects in both males and females. AR concentration was not elevated following 21 days of E treatment to female rats. These data suggested that the increases in AP weight following 21 days of E treatment were masking the effects of E on AP cytosolic AR when expressed on a per milligram protein basis. Consequently, we inhibited E-induced AP growth by the simultaneous administration of bromocriptine (BR). BR was administered concurrently with E to female F344 rats by the implantation of a constant release pellet of BR (25 mg/animal/21 days). Animals were sacrificed 21 days following E treatment. Concurrent BR treatment significantly reduced AP weight and plasma prolactin levels following E treatment and increased the concentration but not the content of AR (p < 0.05). These data demonstrate that increases in AR number in the AP as a result of E exposure is not a consequence of AP growth. This suggests that E-induced increases in AR are not related to lactotroph proliferation.

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

A Characterization of Estrogen’s Influence on Anterior Pituitary Androgen Receptor: Effect of Bromocriptine Treatment

Rodriguez

1991

“…After washing with buffer, the specimens were postfixed for 1 h in 1% phosphate-buffered osmium tetroxide, washed again, incu bated for 30 min in 0.4 M sucrose and then frozen as described previously [6,12,14,15]. Ultrathin sections were cut at -120°C on an Ultrotome III (LKB Stockholm, Sweden) fitted with a Cryokit, as described by Tokuyasu [25].…”

Section: Methodsmentioning

confidence: 99%

Ultrastructural Evidence for Endogenous Somatostatin-Like Immunoreactivity in the Pituitary Gland

Morel

Mesguich

Dubois³

et al. 1983

The tetradecapeptide, somatostatin (SRIF), is a potent inhibitor on pituitary hormone release, by a direct effect. The immunocytological method was used with the aim of localizing SRIF at the cellular and subcellular levels. Rat pituitaries were fixed and frozen. Ultrathin sections, obtained by cryoultramicrotomy, were incubated with anti-SRIF serum. The antigen-antibody reaction was detected by 4-chloro-1-naphthol. SRIF immunoreactivity was observed in somatotrophs, thyreotrophs and prolactin cells, but not in corticotrophs or gonadotrophs. In immunoreactive cells, SRIF was found in the cytoplasmic matrix, in the secretory granules and in the nucleus distributed primarily in the euchromatin, in the vicinity of the heterochromatin regions. SRIF immunoreactivity was also observed at the plasma membrane. No immunoreactivity was observed when nonimmune serum or anti-SRIF serum incubated with SRIF was used. No modification was observed when anti-SRIF serum incubated with gonadoliberin, thyroliberin or vasopressin was used. These data (1) provide immunocytological evidence for the presence of somatostatin in pituitary gland, and (2) indicate the presence of SRIF peptide in the somatotrophs, thyreotrophs and prolactin cells.

“…19 589). This se rum has been studied previously [16]. Anti-porcine luteinizing hor mone (3 (pLHji) serum.…”

Section: Antiseramentioning

confidence: 99%

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

Bégeot¹,

Dupouy

Dubois

et al. 1981

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.