Vascular and Renal Actions of Salmon Calcitonin

When freshwater eels were given either 5 or 15 i.u. calcitonin kg" body weight, there was an increase in dorsal aortic blood pressure as well as a rise in urine volume, glomerular filtration rate and electrolyte excretion rate, 1 h after injection. None of these changes was shown by seawater-adapted eels. When freshwater-adapted eels received 15 i.u. calcitonin kg" body weight there were significant changes in plasma electrolyte levels, again a response not shown by seawater-adapted fish. These changes occurred in 1 h after the injection of hormone, during which time plasma levels of sodium, chloride and calcium fell whilst plasma potassium levels increased. At no time within the first hour were there changes in the relative handling of electrolytes. However, seawater-adapted eels showed hypercalcaemia and a reduced relative calcium clearance 3 h after receiving 15 i.u. calcitonin kg" body weight.