Calcium Accumulation and Respiratory Activity of the Small Intestine of the Rat

The possible dependence of calcium accumulation upon respiratory activity of the rat small intestine has been investigated in vitro. The oxygen consumption of this tissue was relatively insensitive to the concentration of calcium in the medium; and the accumulation of radioactive calcium was greatly dependent upon ambient calcium concentration. At low concentrations of the medium the ratio of tissue calcium to that in the medium greatly exceeded unity, indicating an accumulation of this ion against a concentration gradient. However, this effect was also seen when the tissues were incubated in a gas phase of nitrogen instead of oxygen, demonstrating the lack of dependence of this process on tissue respiration. The rate at which calcium accumulated at 0° also suggests that the accumulation of calcium by the small intestine is not a metabolically controlled process but rather is a binding phenomenon similar to that reported for salivary gland of the rat.