Fish have served as objects of experimental research for several centuries, however their role as an experimental model, which can substitute for conventional laboratory warmblooded animals has been enhanced particularly in recent times. Representative agnathans (lamprey or hagfish) and teleost fish (salmon, trout, catfish) are to be used in studies of the regulation of metabolism and growth by pancreatic hormones, their interaction with each other and with growth hormone and insulin-like growth factor. Specific objectives of the project are: 1) to develop new homologous radioimmunoassays or enzyme- linked immunoassays for measurement of the islet hormones in lampreys; 2) to continue an assessment of the profiles of pancreatic hormones in plasma and endocrine pancreas of salmon, trout and lamprey at different stages of their life cycles and kept under different feeding regimes; 3) to determine the levels of pancreatic hormones in the blood outflow from the pancreatic islets (major producing sites) and from the liver, (important target and main place for destruction of the pancreatic hormones); to evaluate the differences in the hormonal contents in fasting and feeding animals with respect to these patterns; 4) to examine whether the cells from different parts of liver, encountering different levels of hormones are metabolically differentiated and to employ isolated hepatocytes as an experimental in vitro system for investigation of the effects of glucagon-family peptides, which regulate energy stores; 5) to study specific binding of the major anabolic hormone, insulin to its target, the liver, at different developmental stages and under different feeding regimes; 6) to investigate whether the unusual abundance of "big" somatostatins in the endocrine pancreas of lamprey and salmon has any particular physiological significance. The expected results will contribute to better understanding of hormonal regulation of nutrition and growth as well as extend our knowledge of functional evolution of pancreatic hormones in vertebrates.
