Changes in the rates of glycogenesis, glycogenolysis, lipogenesis, and lipolysis in selected tissues of the coho salmon (Oncorhynchus kisutch) associated with parr‐smolt transformation

The rates of glycogenesis, glycogenolysis, lipogenesis and lipolysis were determined in selected tissues of the coho salmon, Oncorhynchus kisutch, during the period of parr‐smolt transformation between February 1983 and June 1983. Glycogen synthesis in the liver, measured by uridine diphosphate formation, decreased 54% from initial levels. Liver glycogen phosphorylase a activity increased by 66%. Neutral lipid (sterol) and fatty acid synthesis in the liver and mesenteric fat was measured by tritium incorporation. Fatty acid synthesis in the liver and mesenteric fat decreased by 88% and 81%, respectively, between late February (parrs) and early June (smolts). There was no significant change in the rate of tritium incorporation into liver or mesenteric fat neutral lipids during the sampling period. Lipolytic rates were assessed by measuring the release of ¹⁴C‐oleic acid from ¹⁴C‐triolein in the presence of partially purified triacylglycerol lipase enzyme preparations from the liver, dark muscle and mesenteric fat. Liver, dark muscle and mesenteric fat lipase activity increased by 86%, 146% and 289%, respectively, during the sampling period. Increased glycogen and lipid breakdown, and concomitant decreased glycogen and fatty acid synthesis would contribute to the lipid and glycogen depletion observed in salmonid species undergoing parr‐smolt transformation.