Received January 19, 2004
Revised February 23, 2004
Accepted after revision April 19, 2004

¹ UCSD School of Medicine,

^* To whom correspondence should be addressed. E-mail: pquinton{at}ucsd.edu.

	Abstract

Effective and specific inhibition of the CFTR Cl^- channel in epithelia has long been needed to better understand the role of anion movements in fluid and electrolyte transport. Until now, available inhibitors have required high concentrations, usually in the mM or high µM range, to effect even an incomplete block of channel conductance. These inhibitors, including NPPB, bumetamide, glibenclamide, DIDS, etc., are also relatively non-specific. Recently a new anion channel inhibitor, a thiazolidinone derivative, termed CFTR_Inh-172 has been synthesized and introduced with apparently improved inhibitory properties as shown by effects on anion conductance expressed in cell lines and on secretion in vivo. Here, we assay the effect of this inhibitor on a purely salt absorbing native epithelial tissue, the freshly isolated microperfused human sweat duct, known for its inherently high expression of CFTR. We found that the inhibitor at a maximum dose limited by its aqueous solubility of 5 µM partially blocked CFTR when applied to either surface of the membrane, but may be somewhat more effective from the cytosolic side (70% inhibition). It may also partially inhibit Na⁺ conductance. The inhibition was relatively slow with a half time for maximum effect of about 3 minutes and showed very slow reversibility. Results also suggest that CFTR Cl^- conductance (G_Cl) was blocked in both apical and basal membranes.

Key Words: Chloride channel, Cystic fibrosis, Inhibition