Regulation of Progesterone Biosynthesis by Androgens and Estrogen in the Domestic Hen

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Dr. Janice Bahr plans to study the regulation of ovulation using the hen as a model system. The domestic hen has a unique egg laying pattern, in that it lays an egg at a later time on sequential days until the last egg is laid late in the afternoon. The hen then skips a day and resets the biological clock so that the first egg of the next sequence of eggs is laid early in the morning. The objective of this continuing research effort is to understand the interplay between the endocrine system, the brain (biological clock) and the reproductive system that gives rise to this unique pattern. The focus of the work is on factors controlling the action of the ovulation inducing hormone, LH, (produced by the pituitary) on the regulation of progesterone production in the granulosa cells in the wall of the follicle. Progesterone surges trigger ovulation from the follicle; therefore, the regulation of progesterone synthesis from estrogens and androgens in these cells is critical in the regulation of ovulation. LH production by the pituitary is regulated by both blood levels of progesterone and estrogen and by releasing factors that are under the control of the hypothalamus (brain). The results are of prime importance to our understanding of the control of ovulation in vertebrate species.