Responses of frog skin, Rana pipiens, calcium ion transport to parathyroid hormone, calcitonin, and vitamin D3.

The responses of cutaneous Ca2+ transport to parathyroid hormone, calcitonin, and vitamin D3 were evaluated in intact Rana pipiens and isolated skins from this species. Parathyroid hormone (12 pmol g-1) stimulated Ca2+ influx in intact frogs but not in isolated skin (10-100 pmol ml-1) unless the frogs had been pretreated with vitamin D3 injections (100-300 microgram day-1) for 3 days prior to isolating the skins for flux measurements. Pretreatment of intact frogs with vitamin D3 for 3 days (100 microgram day-1) also resulted in greater responses to PTH (6-12 pmol g-1). Vitamin D3 (most likely after conversion to 1,25(OH)2D3) had a direct stimulatory effect on Ca2+ transport in isolated skins after three daily doses of 500 microgram of D3. Calcitonin also stimulated Ca2+ influx in both intact frogs (24 pmol g-1) and isolated skins (25-100 pmol ml-1). We conclude that parathyroid hormone, facilitated by vitamin D, stimulates Ca2+ influx in the skin of R. pipiens. We also conclude that calcitonin is stimulatory for cutaneous Ca2+ influx in this species.