Plasma immunoreactive calcitonin in the frog ( Rana pipiens)

Abstract

1. 1. Plasma immunoreactive calcitonin (iCT) and ionic calcium ([Ca]i) were measured in intact frogs ( Rana pipiens) within complete 24 hr light-dark cycles over an 18 month period. 2. 2. Plasma iCT exhibits an annual periodicity about the annual mean of 10.0ng/ml, with an amplitude of 5.4 ng/ml that peaks in October. 3. 3. Within an annual cycle, a significant inverse association exists between the basal monthly levels of plasma iCT and [Ca]i for animals maintained in freshwater control conditions. 4. 4. When subjected to a high calcium environment during the latter half of the year, plasma [Ca]i and iCT were elevated above control levels but exhibited independent cyclic patterns. 5. 5. A distinct seasonal response of increased iCT in a high calcium environment may be related to the secretory activity of the ultimobranchial glands and physiological responsiveness to other calcémie hormones; e.g. parathyroid hormone and vitamin D.