Calcitonin stimulates H+ secretion in rat kidney intercalated cells

Calcitonin (CT) modulates rat intercalated cell (IC) functions of the rat cortical collecting duct (CCD) [E. Siga, B. Mandon, N. Roinel, and C. de Rouffignac. Am.J. Physiol. 264 (Renal Fluid Electrolyte Physiol. 33): F221-F227, 1993]. To characterize the specific function regulated by CT, rat CCDs were perfused in vitro. Total CO2 net fluxes (JtCO2, pmol.mm-1.min-1) and transepithelial voltage (Vt) were measured. Bath CT induced a significant tCO2 reabsorption. This effect was higher on CCDs harvested from acid-loaded than from control rats. When HCO3- secretion was blocked, CT also raised JtCO2 and Vt. When H+ secretion was blocked, CT was ineffective on JtCO2 and Vt. When HCO3- secretion was increased and H+ secretion was inhibited, CT did not change JtCO2, whereas isoproterenol (ISO) increased tCO2 secretion from -13.5 +/- 2.0 (control) to -19.0 +/- 2.4 (ISO). In rat CCD studied under these same preceding conditions plus luminal amiloride to block the Na(+)-dependent Vt, CT did not alter Vt, whereas ISO increased it by 4.5 +/- 0.7 mV. We conclude from these data that, in the rat CCD, calcitonin stimulates H+ secretion, likely by so-called alpha-intercalated (alpha-IC) cells, whereas ISO stimulates HCO3- secretion, likely by so-called beta-IC cells.