PTH stimulates a Cl-dependent and EIPA-sensitive current in chick proximal tubule cells in culture

The electrophysiological effects of parathyroid hormone (PTH) were studied in a primary cell culture model of the chick (Gallus domesticus) proximal tubule. In this model, confluent monolayers are grown on permeable filters and exhibit vectorial transport, including glucose-stimulated current. Under short-circuit conditions, PTH, at 10−9 M, induced a positive current [short-circuit current (I sc)] response, with an average 2-min peak response of 14.30 ± 1.58 μA/cm2 over the baseline I sc, followed by a slow decay. The PTH response was dose dependent, with a half-maximal response at 5 × 10−9 M and maximal response at 5 × 10−8M. Forskolin and dibutyryl-cAMP also stimulatedI sc, as did the phosphodiesterase inhibitor IBMX. In contrast, the phorbol ester PMA inhibited baselineI sc. The PTH response was nearly abolished by apical addition of 100 μM EIPA, an inhibitor of Na+/H+ exchangers, and partially blocked by the Cl− channel blockers 5-nitro-2-(3-phenylpropylamino)benzoic acid (NPPB; 100 μM) and glibenclam...