Vitamin B-6 deficiency alters rat enterocyte calcium homeostasis but not duodenal transport

Isolated enterocytes were used as differential transporting cells to examine calcium homeostasis in control and vitamin B-6-deficient rats. Kinetic analysis of calcium fluxes, as well as biochemical determinations, indicated that enterocytes from control animals had high concentrations of cytosol ionized calcium (318.5 +/- 22.4 nmol/L) and a large pool of exchangeable calcium (2.72 nmol/mg protein, or 86% of total cell calcium). Vitamin B-6 deficiency resulted in a 44% reduction in total cellular calcium (1.71 +/- 0.24 vs. 3.07 +/- 0.29 nmol/mg protein), a 69% reduction in total exchangeable calcium (0.85 vs. 2.72 nmol/mg protein) and a 56% reduction in cytosol ionized calcium concentration (141.4 +/- 13.5 vs. 318.5 +/- 22.4 nmol/L). Calcium fluxes between all cellular compartments were markedly diminished as a result of vitamin B-6 deficiency. However, vitamin B-6 deficiency did not affect the basic morphological or functional features of the enterocytes, such as cell viability, cell volume, membrane permeability and protein content. Moreover, intestinal calcium transport in vivo was not affected during vitamin B-6 deficiency, perhaps due to the greater paracellular ion movement compensating for the lower transcellular transport.