Baldwin G F, Bentley P J
J Exp Biol. 1980 Oct;88:357-65. doi: 10.1242/jeb.88.1.357.
Non-feeding bullfrog (Rana catesbeiana) tadpoles can maintain their body Ca concentration in artificial pond waters containing a range of Ca concentrations. The rate of uptake of 45Ca increases when the tadpoles are pre-adapted to a low-Ca pond water and declines when they are pre-adapted to high Ca. Measurement of drinking rate shows that drinking could account for only 5% of the influx. From in vitro experiments, it is estimated that about 70% of the influx occurs accoss the gills, and about 25% through the skin. Calcitonin decreases accumulation of 45Ca while 1,25-(OH)2 vitamin D3 increases it; parathyroid hormone was without effect. Efflux of 45Ca was unchanged by calcitonin or parathyroid hormone.
不摄食的牛蛙蝌蚪能够在含有一系列钙浓度的人工池塘水中维持其体内钙浓度。当蝌蚪预先适应低钙池塘水时，45Ca的摄取速率增加，而当它们预先适应高钙环境时，摄取速率下降。饮水速率的测量表明，饮水仅占钙流入量的5%。通过体外实验估计，约70%的钙流入是通过鳃进行的，约25%是通过皮肤。降钙素会降低45Ca的积累，而1,25-(OH)2维生素D3会增加其积累；甲状旁腺激素则没有作用。降钙素或甲状旁腺激素对45Ca的流出没有影响。
