Characterization of the second messengers involved in 1α,25-dihydroxyvitamin D(3) stimulated intestinal calcium absorption (transcaltachia).

1α,25-Dihydroxyvitamin D(3) [1α,25(OH)(2)D(3)] has been shown to generate biological responses via both genomic and nongenomic pathways. In the nongenomic process, 1α,25(OH)(2)D(3) stimulates the rapid transport of Ca(2+) across the chick intestinal epithelial cell, a process termed transcaltachia. In previous studies, the involvement of Ca(2+)-channels, protein kinase C, and cAMP-dependent kinase in the 1α,25(OH)(2)D(3) stimulated transcaltachic response have been implicated. To further characterize the elements involved in mediating the transcaltachic effect, H7, an inhibitor of protein kinase C, U73122, an inhibitor of phospholipase C, and mastoparan, an activator of G-proteins, were employed. Both H7 and U73122 suppressed 1α,25(OH)(2)D(3) stimulated intestinal Ca(2+) transport. Mastoparan was found to mimic the effect of 1α,25(OH)(2)D(3) to stimulate transcaltachia. Collectively, these results suggest that 1α,25(OH)(2)D(3) activations of G-proteins, phospholipase C and protein kinases are essential steps in the rapid stimulation of intestinal Ca(2+) transport.