IMMUNOHISTOCHEMICAL EVIDENCE THAT FOLLICLE-STIMULATING HORMONE AND LUTEINIZING HORMONE RESIDE IN SEPARATE CELLS IN THE CHICKEN PITUITARY

Authors: Proudman, John; VANDESANDE, F - CATHOLIC U.LEUVEN BELGIUM; BERGHMAN, L - CATHOLIC U.LEUVEN,BELGIUM

Submitted to: Biology of Reproduction
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/12/1999
Publication Date: N/A
Citation: N/A

Interpretive Summary: Two hormones, produced by the pituitary gland, are particularly critical to regulating the growth and ovulation of follicles on the ovary. Thus, the optimum production and secretion of these hormones is central to the efficient productions of eggs and embryos. Previous research has shown that these two hormones, luteinizing hormone (LH) and follicle-stimulating hormone (FSH), are produced within the same pituitary cells in all species (ranging from humans to frogs) studied to date- except the bovine, where LH and FSH reside in separate cells. Since these hormones function independently during reproduction, a major unanswered question in reproductive biology is how the production and secretion of these hormones is independently regulated. The cellular location of these hormones had never been established in any avian species. Since LH and FSH are structurally very similar, we produced three monoclonal antibodies to chicken FSH which were absolutely specific for this hormone and did not bind to LH. Using dual-label fluorescent techniques to identify chicken pituitary cells containing FSH and/or LH, we demonstrated that these hormones are located almost exclusively in separate cells. FSH-containing cells were less numerous than LH-containing cells, and were distributed differently within the gland. Our results show that the chicken is similar to the bovine in being the only species know to store LH and FSH in separate cells within the pituitary. This finding suggests that the chicken may be an important and inexpensive model for the study of the independent regulation of LH and FSH secretion. Scientists may use this information to better understand how the production of gametes is regulated by the brain and pituitary.

Technical Abstract: As is the case in other tetrapod species, the chicken gonadotropins LH and FSH consist of a common alpha-subunit and a hormone-specific beta-subunit. Gonadotrophs containing LH were shown earlier to be distributed throughout both the caudal and cephalic lobes of the chicken anterior pituitary, but the cellular distribution of FSH in avian species is still uncertain. The purpose of this study was to determine the cellular distribution of FSH- containing chicken gonadotrophs by use of FSH-specific monoclonal antibodies. Three new monoclonal antibodies towards chicken FSH were proven hormone-specific by immunodetection of purified hormones on dot blots and by dual-label immunohistochemistry on sagittal sections of chicken pituitaries. A rabbit antibody was used to detect chicken LH. Results showed that LH-containing gonadotrophs were densely distributed throughout the anterior pituitary, while gonadotrophs containing FSH were much less numerous and, while also present in both lobes, FSH-positive cells were largely absent from the outer margin of the gland. Dual-label immunohistochemistry revealed that LH and FSH reside almost exclusively in separate gonadotrophs. The identity of FSH-containing cells was further confirmed by using an antibody to the chicken alpha-subunit, which showed that FSH immunoreactivity was always co-localized with the alpha-subunit. Our results suggest the possibility that production and secretion of LH and FSH may be regulated differently in chickens than in most other species studied to date.