Diurnal variations of calcium transport in the small intestine of adrenalectomized, nephrectomized, and vitamin D-treated rats.

Everted gut-sac-technique was used to study diurnal periodicity of active calcium transport in the small intestine of the adult rat maintained under 12:12 hours light-dark cycle. Similar to intact rats, diurnal fluctuations of the transport capacity persisted in adrenalectomized animals and in rats treated with 100,000 units of vitamin D3. Bilateral nephrectomy resulted in significant dampening of diurnal transport fluctuations. In contrast to the differences in calcium transport, diurnal changes of the calcium binding protein did not appear to be statistically significant when investigated in the intact, vitamin D-treated and nephrectomized rats.