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 D3were evaluated in intactRana pipiensand 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 D3injections (100–300 μg day−1) for 3 days prior to isolating the skins for flux measurements. Pretreatment of intact frogs with vitamin D3for 3 days (100 μg 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 μg 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 ofR. pipiens. We also conclude that calcitonin is stimulatory for cutaneous Ca2+influx in this species.