Calcitonin-like immunoreactivity has been demonstrated by immunofluorescence in the cells of the ultimobranchial gland of two species of
Rana, using an indirect (sandwich) technique with anti-pure porcine calcitonin serum. The possibility of cross-reactivity, between the amphibian hormone and anti-porcine calcitonin antibody, had been anticipated on account of the observation that injected porcine calcitonin lowered the plasma calcium levels in one of the species under investigation.