DIURNAL VARIATIONS IN THE INFLUENCE OF THE ULTIMOBRANCHIAL GLANDS ON CALCIUM HOMEOSTASIS IN THE FROG ( RANA PIPIENS )

Abstract

The effect of the light-darkness cycle on the efficiency of the ultimobranchial and parathyroid glands in altering duodenal calcium transport and plasma and urinary concentrations of calcium was examined in the adult male frog (Rana pipiens). Frogs were unfed, but were allowed access to 0.05 M-CaCl2 in the surrounding medium after ultimobranchialectomy or parathyroidectomy. Calcium transport, as assayed by the everted gut-sac technique, was increased in ultimobranchialectomized frogs at sunrise, concomitant with acute hypercalcaemia and hypercalciuria. An opposite but chronic response was observed in parathyroidectomized frogs with intact ultimobranchial glands. The maximum response observed at sunrise occurred when the concentration of calcium in the plasma of control frogs was decreasing; the minimum response, which occurred 6 h after sunrise, was coincident with a diurnal peak in the concentration of calcium. Vitamin D3 (500 microgram/frog) enhanced calcium transport in ultimobranchialectomized frogs, which resulted in chronic hypercalcaemia and hypercalciuria. The results suggest that diurnal variations in the plasma concentration of calcium do not initiate ultimobranchial activity, but are a response to endocrine control synchronized with the transition from darkness to light.

Amphibian parathyroids: Morphological and functional aspects

“…It seems that both PTH and prolactin are involved in calcium regulation in anuran tadpoles. PTX frogs exhibited a 20% decrease in plasma ionic calcium (Robertson, 1986) as well as a 30% decrease in duodenal calcium transport (Robertson, 1975(Robertson, , 1978(Robertson, , 1993. A study of the effect of PTH on calcium transport in epithelial cells of the intestine is lacking.…”

Amphibian parathyroids: Morphological and functional aspects

“…It seems that both PTH and prolactin are involved in calcium regulation in anuran tadpoles. PTX frogs exhibited a 20% decrease in plasma ionic calcium (Robertson, 1986) as well as a 30% decrease in duodenal calcium transport (Robertson, 1975(Robertson, , 1978(Robertson, , 1993. A study of the effect of PTH on calcium transport in epithelial cells of the intestine is lacking.…”

Amphibian parathyroids: Morphological and functional aspects

“…It seems that both PTH and prolactin are involved in calcium regulation in anuran tadpoles. PTX frogs exhibited a 20% decrease in plasma ionic calcium (Robertson, 1986) as well as a 30% decrease in duodenal calcium transport (Robertson, 1975(Robertson, , 1978(Robertson, , 1993. A study of the effect of PTH on calcium transport in epithelial cells of the intestine is lacking.…”

Amphibian parathyroids: Morphological and functional aspects

“…It seems that both PTH and prolactin are involved in calcium regulation in anuran tadpoles. PTX frogs exhibited a 20% decrease in plasma ionic calcium (Robertson, 1986) as well as a 30% decrease in duodenal calcium transport (Robertson, 1975(Robertson, , 1978(Robertson, , 1993. A study of the effect of PTH on calcium transport in epithelial cells of the intestine is lacking.…”