Antibodies to Porcine Thyrocalcitonin: Effects on the Hypocalcemic Activity of Calf, Rat and Monkey Thyroid Extracts

Publisher Website
Google Scholar
Abstract
Two rabbits were repeatedly injected with partially purified thyro-calcitonin, a hypocalcemic principle extracted from porcine thyroid glands. The hypocalcemic activity of porcine thyrocalcitonin in the intact rat was neutralized completely by incubation with serum obtained from the injected rabbits. No loss of hypocalcemic activity occurred during incubation of thyrocalcitonin with control rabbit sera. It is tentatively concluded, on the basis of the following evidence, that the factor in the serum of the injected rabbits that neutralized the hypocalcemic activity of thyrocalcitonin is antibody to thyrocalcitonin: the titer of the neutralizing factor in rabbit serum was shown to rise with repeated injections of thyrocalcitonin; hypocalcemic activity was recovered from the precipitate which formed during incubation of thyrocalcitonin with immune rabbit serum; the factor did not indiscriminately neutralize the hypocalcemic activity present in extracts of thyroid glands obtained from all species; It was stable to heating at 60 C for 20 min; Serum from immunized rabbits, but not from normal rabbits, fixed complement with purified thyrocalcitonin. Despite complete neutralization of the hypocalcemic activity of porcine thyrocalcitonin by antiporcine thyrocalcitonin diluted 1: 2, no neutralization of the hypocalcemic activity in rat or monkey thyroid extracts occurred during incubation with undiluted antiporcine thyrocalcitonin. However, undiluted antiporcine thyrocalcintonin neutralized completely the hypocalcemic activity of an extract of calf thyroid glands. These findings demonstrate that porcine thyrocalcitonin can elicit antibody formation in the rabbit, and they constitute the first immunochemical evidence of structural differences between thyrocalcitonins obtained from animals of different taxonomic orders.