Abstract
Summary
A seasonal covariation in calci-tonin and serotonin content of bat thyroid has been found. Whereas the mean level of thyroidal calcitonin in active bats ranged between 30 and 48 MRC mU/mg of protein, a two- to threefold increase in this level was observed prior to and during early hibernation. Associated with this increase, a relative hypocalcemia was observed. In late hibernation, thyroidal calcitonin level returned to the range observed in active bats. A parallel seasonal profile was found for bat thyroid serotonin content, which varied from a mean of 4.1 μg/g during the active phase of the annual life cycle to a peak close to 13 μg/g observed in early hibernation. The seasonal covariation of calcitonin and serotonin reflects ultrastructural changes observed in the secretory granules of thyroid parafollicular cells during the annual life cycle of the bat.
The authors wish to acknowledge the competent technical assistance rendered by Mary Ann Viloria and John Patrikes.
This work was supported in part by USPHS Grant No. AM11431 and by a grant from Ciba-Geigy Corporation, Summit, New Jersey.
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