[Dependence of calcium absorption in the chicken small intestine on its Ca2+-binding protein content and the effect of exogenous nucleotide precursors on this process].

A dependence was studied between the level of calcium absorption and the content of calcium-binding protein in the small intestine of D-hypovitaminous chickens to whom different exogenic precursors of nucleotides (potassium orotate or guanine) were administered at different stages of the response (0-72 h) to a single administration of vitamin D3 in a dose of 500 MU. It is established that under the effect of potassium orotate or guanine the degree of discrepancy between calcium adsorption and the content of Ca2+-binding protein increases at all stages under investigation. The results of the mathematical analysis of the experimental data which is based on the supposition of the linear dependence between the level of absorbed calcium and Ca2+-binding protein evidence for a considerable rise in the excess amount of the latter, which possibly does not take part in cation absorption, in the chickens who were administered nucleotide exogenic precursors. The data obtained show that the amount of calcium-binding protein is not a limiting factor in the mechanism of vitamin D3 stimulation of calcium absorption in the chicken small intestine.