Properties of a Cl−‐Conductive Pathway(s) in Microsomes from Rat Kidney Inner Medulla

The properties of a protein-kinase-A(PKA)-activated Cl−-conductive pathway(s) in alkaline phosphatase-enriched microsomes from the rat inner medulla (IMV) were investigated. Transcripts of cystic fibrosis transmembrane regulator (CFTR) were detected by reverse transcription/polymerase analysis of total RNA from the inner medulla, while immunoblot analysis using anti-CFTR antibodies detected a 170-kDa protein in the IMV. The PKA Cl− conductive pathway(s) was studied by measuring the rate of valinomycin-induced microsomal swelling by light scattering. PKA increased the rate of valinomycin-induced swelling of vesicles consistent with the presence of Cl−-conductive pathway(s). The pharmacological properties and anion selectivity of the PKA-activated Cl− -conductive pathway(s) were similar to those of the CFTR Cl− channel. Our results show that a CFTR Cl− channel and possibly another cAMP-activated pathway(s) may participate in Cl− secretion in the rat inner medulla.