Hormonal regulation of mineral metabolism in fishes and invertebrates

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The current proposal seeks to continue our long term program of studies on how calcium and phosphate homeostasis are regulated in fish and aquatic leeches by the peptide hormone, stanniocalcin-1 (STC-1).Objective I. The mitochondria-rich, chloride cells in trout gill have high levels of STC-1 receptors. We will explore the possibility that STC-1 is targeted to chloride cell mitochondria as part of the mechanism of action by which STC-1 inhibits gill calcium transport.  Objective II. Early oocytes in trout ovary produce a variant form of STC-1 that appears to be targeted back to these oocytes in an autocrine or intracrine loop. We seek to identify the sub-cellular compartment targeted by the hormone and to purify the  variant form of STC-1 for chemical analysis and bioassay.Objective #3. Leeches have STC-related proteins and receptors that regulate calcium uptake by the skin. We will study the regulation of this transport process by factors such as calcium. We will also determine if calcium uptake in leeches cyclical over time (weeks), as it is in fishes. We will also purify two different leech forms of STC, characterize then structurally and test them in biological studies.