Abstract
The effects of calcitonin-like factor and calcitonin were compared in rats treated under various conditions. The hypocalcemic effect of this factor was stronger in rats fed with low-calcium diet than those fed with normal diet, and its effect did not alter by prior parathyroidectomy, though it was abolished by thyroparathyroidectomy. Calcitonin-like factor had a weak hypophosphatemic effect since it did not decrease serum phosphate under various conditions, especially this factor did not diminish hyperphosphatemia induced by parathyroidectomy, and the addition of phosphate did not increase the hypocalcemia effect of this factor. It may be suggested that this factor is different from calcitonin in hypophosphatemic action and this factor did not act by releasing calcitonin from the thyroid gland. This factor inhibited the amount of total hydroxyproline released from metaphysis into the medium, so that calcitonin-like factor seems to give the hypocalcemic effect primarily through the inhibition of bone resorption.
