Robertson D R
J Endocrinol. 1978 Nov;79(2):167-78. doi: 10.1677/joe.0.0790167.
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.
在成年雄性青蛙（豹蛙）中，研究了明暗周期对鳃后腺和甲状旁腺改变十二指肠钙转运以及血浆和尿液钙浓度效率的影响。青蛙未喂食，但在切除鳃后腺或甲状旁腺后，可在周围介质中获取0.05 M氯化钙。通过外翻肠囊技术测定，切除鳃后腺的青蛙在日出时钙转运增加，同时伴有急性高钙血症和高钙尿症。在鳃后腺完整的甲状旁腺切除青蛙中观察到相反但慢性的反应。在日出时观察到的最大反应发生在对照青蛙血浆钙浓度下降时；日出后6小时出现的最小反应与钙浓度的昼夜峰值一致。维生素D3（500微克/只青蛙）增强了切除鳃后腺青蛙的钙转运，导致慢性高钙血症和高钙尿症。结果表明，血浆钙浓度的昼夜变化并非引发鳃后腺活动的原因，而是与从黑暗到光明转变同步的内分泌控制的一种反应。
