Metabolism of Circulating Hormones by the Fish Gill

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Previous research in this laboratory has shown that the fish gill, like the mammalian lung, has the unique ability to regulate the concentration of a variety of hormones in blood through specific activation and inactivation processes. All blood pumped by the fish heart must first pass through the gills before it is distributed to the rest of the body. Thus the gill is in an ideal location to effectively serve as a biological blood filter, and indeed, the PI has shown that the efficiency of hormone metabolism by the gill may exceed 90%. The proposed research will examine the mechanisms through which the gill metabolizes several important blood pressure regulating hormones, catecholamines, angiotensin and atrial natriuretic peptide. Preliminary studies have also shown that these same mechanisms may be involved in degradation of toxic substances and these studies will be continued. This project is significant for several reasons: 1. Information derived from these studies will further our understanding of endocrine control systems in lower vertebrates. 2. Due to the similarity between gills and lungs the present work will provide insight into the evolution of the lung as a metabolic organ and the mechanisms of pulmonary metabolism. These studies also illustrate the potential of the gill as an alternative, non-mammalian model in biomedical research. 3. Evaluation of the gill as an organ for detoxification has not been critically examined. Our preliminary work indicates that the gill may also be an important tool in environmental studies.