Parathyroid hormone stimulates calcium transport in perfused duodena from normal chicks: comparison with the rapid (transcaltachic) effect of 1,25-dihydroxyvitamin D3.

Both 130 pM 1,25(OH)2D3 and 130 pM bPTH 1-34 were found to stimulate calcium transport in perfused, isolated duodenal loops from normal, vitamin D-replete birds. Within 2 min of vascular perfusion with the seco-steroid. 45Ca transport increased to 153% of controls (P less than 0.01), whereas significant stimulation by the peptide hormone was not observed until after 12 min of exposure (142% of controls, P less than 0.05). The inactive peptide analogue, bPTH 3-34, failed to alter calcium transport rates from those observed in vehicle controls. The final magnitude of the effect observed for either 1,25(OH)2D3 or bPTH 1-34 was similar in that each hormone enhanced the appearance of 45Ca in the venous effluent to greater than 200% of controls. This work is the first to report a direct effect of PTH on calcium transport in the intestine, as well as a greater rapidity in the response of perfused duodena to 1,25(OH)2D3 than previously observed. On the basis of these findings we propose the term transcaltachia to denote the rapid stimulatory effect of a hormonal agonist on calcium transport across the intestine.