Regulation of Adrenal Steroidogenesis in Birds

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The bird adrenal gland is capable of synthesizing several cortisone-like hormones. One of these is responsible for the regulation of certain aspects of carbohydrate metabolism in the organism, while another acts on the kidney to ensure proper salt and water balance. Cells isolated from the gland respond to incubation media containing the pituitary hormone, corticotropin by producing the two types of cortisone-like hormone. The cells also respond to incubation media containing a hormone called angiotensin II. Under these circumstancs, they produce relatively large amounts of the salt- and water regulating hormone, but none of the carbohydrate-regulating hormone. These effects of corticotropin and angiotensin II on isolated tissue samples simulate the responses of the adrenal gland in organisms subjected to stress and diets containing different levels of salts. Until a few years ago, it was assumed that the secretion of these hormones was controlled exclusively by corticotropin and angiotensin II but evidence has recently accumulated to indicate that factors of neural origin may also act, to regulate the synthesis and release of adrenal steroid hormones. Nerve cells terminating in the adrenal gland contain, and may secrete, a variety of polypeptides, in addition to the typical adrenalin-like hormones. The proposed studies will contribute to our understanding of the ways in which regulators derived from nerve cells influence the overall control of adrenal steroid hormone synthesis. The experimental model will be the developing adrenal gland in the duck embryo. Through the use of the latest ultrastructural, histochemical and immunocytochemical techiques the nature, the loci and the distribution of the adrenalin-like and peptide factors will be investigated. At the same time the functional development and responsiveness of the adrenal steroidogenic cells during embryonic development will be assessed in terms of their secretory and synthetic properties. Since the hormones produced by the adrenal gland are absolutely essential to the survival of all vertebrates, including Man, it is important to understand the nature of the control mechanisms involved in the regulation of this important endocrine gland. Also, knowledge of how these glands function in birds is not only of fundamental interest to the biologist, it is also important to society in general, for birds constitute an important source of food for many millions of people around the world.//