The long-term objective of research proposed in this application is to gain sufficient knowledge about the synthesis and secretion of gonadotropic hormones to allow pharmacological manipulation without adverse side effects. To develop novel strategies for contraception, as well as efficacious treatments for hypothalamic-pituitary hypogonadism it is essential to obtain a more in-depth understanding of the mechanisms for regulation of gonadotropin synthesis and secretion in females by gonadotropin-releasing hormone (GnRH), estradiol, progesterone and inhibin. To this end, the specific aims are to determine if: 1) degradation of mRNAs for gonadotropin subunits by ribonucleases in pituitary cytosol is hormonally regulated; 2) the frequency at which pulses of GnRH are administered affects the rate of accumulation of luteinizing hormone (LH) in the anterior pituitary gland; 3) physiological concentrations of estradiol differentially regulate mRNAs for subunits of gonadotropins and secretion of LH and follicle-stimulating hormone (FSH); 4) synthesis and insertion of GnRH-receptors into the plasma membrane is dependent on RNA and protein synthesis, and microtubule and/or microfilament function. Quantification of hormones in blood and/or pituitary tissue (by radioimmunoassay), of GnRH receptors in pituitary membranes or cells (by a standard curve technique) and of mRNAs for gonadotropins (by solution hybridization) will be performed in most experiments. We have chosen the ewe for the proposed studies due to the extensive background information, the ability to collect frequent blood samples for extended periods, the large pituitary permitting multiple analyses on tissue from a single animal, and the similarity of mechanisms regulating reproductive function between ewes and women. The proposed research will provide new insight into the regulation of gonadotroph sensitivity (GnRH-receptors), differential control of LH and FSh production and secretion, accumulation of LH in the anterior pituitary, and if the degradation of gonadotropin subunit mRNAs is under hormonal control. Such information is essential for developing more efficient and safer methods to regulate fertility in humans and meat- and milk-producing domestic animals. The results should also aid in the design of more efficacious treatments for medical problems associated with gonadotropin synthesis and/or release.
