MICROTUBULE DISRUPTION INHIBITS AVT-STIMULATED CL- SECRETION BUT NOT NA+ REABSORPTION IN A6 CELLS

The effects of microtubule disruption on arginine vasotocin (AVT)-stim ulated Na+ and Cl- transport were studied in A6 cells by measuring sho rt-circuit currents (I-sc) across cell layers grown in tissue culture on permeable supports. Microtubule disruption inhibited an AVT-stimula ted secretory Cl- current but did not prevent activation of amiloride- sensitive Na+ transport. This AVT-stimulated secretory Cl- current was significantly inhibited by glibenclamide, an inhibitor of the cystic fibrosis transmembrane conductance regulator (CFTR). Reverse transcrip tion of RNA isolated from A6 cells followed by polymerase chain reacti on (PCR) using primers designed to amplify a portion of the R-domain o f CFTR cloned from Xenopus laevis skin and immunocytochemistry demonst rated the presence of CFTR in A6 cells and an apparent recruitment of cytoplasmic CFTR to the apical cell surface after AVT stimulation. In contrast, indirect immunofluorescent labeling of Na+ channels using a polyclonal antibody raised against a biochemically isolated Na+ channe l complex from bovine renal medulla labeled the apical plasmamembrane but failed to demonstrate intracellular labeling of Na+ channels (exce pt in subconfluent cells) or recruitment of Na+ channels to the apical membrane region after AVT stimulation.