The long term objective of this project is to determine the importance of pulsatile delivery of gonadotropins to the development and function of rat ovarian cells. This objective is being approached through use of a perfusion system that can mimic closely conditions in vivo, exert precise control of gonadotropic input to cultured ovarian cells, and monitor the responses of the cells to the applied input signals. The perfusion system will be used to study the effects of providing trains of gonadotropic pulses to granulosa cells and intact follicles. Pulse trains to be studied will be ones that closely mimic those observed in the intact rat, in terms of frequency, amplitude and shape. Specifically it is proposed to test: if pulsatile gonadotropins have control advantages over constant concentrations of gonadotropins with amplitude and frequency being inversely related; if each pulse of gonadotropin induces a degree of refractoriness that is related in some fashion to the concentration/duration of the applied gonadotropic pulse if for maximally effective restimulation, the magnitude and duration of this refractoriness dictate the optimal time and amplitude of a subsequent gonadotropic pulse; and if these stimulus-response relationships differ for different ovarian cell types, are affected by prior cellular development or are modulated by steroids and other hormones/factors acting in a paracrine fashion. Response parameters to be measured include steroid secretion (by solid phase immunoassay), release of protons and electroactive molecules, presumably ascorbic acid (by ion selective potentiometry and amperometric cyclic voltammetry), and morphology (by light and electron microscopy). When the envisioned experiments are completed important information regarding gonadotropin amplitude-frequency relationships in controlling follicular function and development should be at hand. This includes obtaining a better understanding both of some of the intraovarian events operating in a paracrine fashion and of the nature of granulosa-the ca cell interactions that extend beyond provision of steroidogenic substrate and product. In addition, a better understanding should be obtained of the role that desensitization plays in determining these response relationships, whether or not each physiological pulse is associated with some degree of desensitization, and whether or not the resulting refractoriness is related to the size of the stimulating pulse. The analyzed and interpreted results should help investigators to decode trains of gonadotropin pulses: recognize and separate important from non-important information, and decipher why similar trains appear to, act differently to control the development and function of ovarian follicles and their contained granulosa cells.

Agency
National Institute of Health (NIH)
Institute
Eunice Kennedy Shriver National Institute of Child Health & Human Development (NICHD)
Type
Research Project (R01)
Project #
2R01HD018018-04
Application #
3315008
Study Section
Reproductive Biology Study Section (REB)
Project Start
1985-03-01
Project End
1991-11-30
Budget Start
1988-12-01
Budget End
1989-11-30
Support Year
4
Fiscal Year
1989
Total Cost
Indirect Cost
Name
University of Michigan Ann Arbor
Department
Type
Schools of Medicine
DUNS #
791277940
City
Ann Arbor
State
MI
Country
United States
Zip Code
48109
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Heinze, K; Keener, R W; Midgley Jr, A R (1998) A mathematical model of luteinizing hormone release from ovine pituitary cells in perifusion. Am J Physiol 275:E1061-71
Midgley Jr, A R; McFadden, K; Ghazzi, M et al. (1997) Nonclassical secretory dynamics of LH revealed by hypothalamo-hypophyseal portal sampling of sheep. Endocrine 6:133-43
Padmanabhan, V; McFadden, K; Mauger, D T et al. (1997) Neuroendocrine control of follicle-stimulating hormone (FSH) secretion. I. Direct evidence for separate episodic and basal components of FSH secretion. Endocrinology 138:424-32
Cantor, H C; Padmanabhan, V; Favreau, P A et al. (1996) Use of newly designed microperifusion system with amperometric sensors for near-continuous on-line monitoring of hormone secretion. I. correlation with the luteinizing hormone secretory response to gonadotropin-releasing hormone. Endocrinology 137:2782-90
Brand, R M; Lyons, R H; Midgley, A R (1994) Understanding the dynamics of cellular responsiveness to modifications of metabolic substrates in perifusion. J Cell Physiol 160:10-6
Wiesen, J F; Midgley Jr, A R (1994) Expression of connexin 43 gap junction messenger ribonucleic acid and protein during follicular atresia. Biol Reprod 50:336-48
Brand, R M; Ghazzi, M N; Rolfes-Curl, A et al. (1994) Continuous on-line hydrogen ion monitoring to study flow dynamics of perifusion systems and cellular metabolism. Am J Physiol 266:E739-49
Brand, R M; Midgley, A R; Williams, W J (1994) Convolution: a method for data analysis in perifusion systems. Am J Physiol 267:E759-68
Wiesen, J F; Midgley Jr, A R (1993) Changes in expression of connexin 43 gap junction messenger ribonucleic acid and protein during ovarian follicular growth. Endocrinology 133:741-6

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