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

Abstract

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 stimulated I sc, as did the phosphodiesterase inhibitor IBMX. In contrast, the phorbol ester PMA inhibited baseline I 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 glibenclamide (300 μM). Higher doses of EIPA or NPPB alone (500 μM) were almost fully effective, with no or slight additional effects of NPPB or EIPA, respectively. The anion exchange inhibitor DIDS (100 μM) and the Na+ channel blocker amiloride (10 μM) had no effect. Bilateral reduction of Cl− in the buffer, from 137 to 2.6 mM, abolished the PTH response; increasing Cl−concentration restored the I sc response, with a half-maximal effect at 50 mM. These data suggest that, in the chick proximal tubule, PTH activates both an Na+/H+exchanger and a Cl− channel that may be functionally linked.

Gene structure, transcripts and calciotropic effects of the PTH family of peptides in Xenopus and chicken

“…Similar effects on the short-circuit current in the same range of PTH concentrations have previously been observed with A6 cells derived from Xenopus kidney [54]; on sodium transport of PT cells derived from chicken kidney [55]; and with PTHrP on fish intestine [56]. Our results further substantiate the effect of the PTH family of proteins on the short-circuit current and suggest that the action of the different peptides on the short-circuit current is tissue dependent and may vary with species.…”

A role for the cystic fibrosis transmembrane conductance regulator in the nitric oxide-dependent release of Cl− from acidic organelles in amacrine cells

“…For example, CFTR inh -172 has little inhibitory effect on shark CFTR but is effective (in order of declining effectiveness) on human, killifish, and pig CFTR (Stahl et al 2012). Limited information is available on chicken CFTR; however, 300 M glibenclamide has been shown to partially inhibit a current that is elicited by parathyroid hormone and is dependent on Cl Ϫ (Laverty et al 2003), and CFTR inh -172 (20 M) has been shown to inhibit CFTR (Laverty et al 2012) in chicken proximal tubule monolayers. Functional differences between human and chicken have been observed for CFTR single-channel currents measured in planar bilayers (Aleksandrov et al 2012).…”