Effects of ouabain and temperature on cell membrane potentials in isolated perfused straight proximal tubules of the mouse kidney

Abstract

In isolated perfused segments of the mouse proximal tubule, the potential difference across the basolateral cell membrane (PDbl) was determined with conventional microelectrodes. Under control conditions with symmetrical solutions it amounted to -62 +/- 1 mV (n = 118). The potential difference across the epithelium (PDte) was -1.7 +/- 0.1 mV (n = 45). Transepithelial resistance amounted to 1.82 +/- 0.09 k omega cm (n = 28), corresponding to 11.4 +/- 0.6 omega cm2. Increasing bath potassium concentration from 5 to 20 mmol/l depolarized PDbl by +24 +/- 1 mV (n = 103), and PDte by +1.6 +/- 0.1 mV (n = 19). Thus, the basolateral cell membrane is preferably conductive to potassium. Rapid cooling of the bath perfusate from 38 degrees C to 10 degrees C led to a transient hyperpolarization of PDbl from -60 +/- 1 to -65 +/- 1 mV (n = 21) within 40 s followed by gradual depolarization by +18 +/- 1% (n = 14) within 5 min. The transepithelial resistance increased significantly from 1.78 +/- 0.11 k omega cm to 2.20 +/- 0.21 k omega cm (n = 15). Rapid rewarming of the bath to 38 degrees C caused a depolarization from -61 +/- 2 mV (n = 17) to -43 +/- 2 mV (n = 16) within 15 s followed by a repolarization to -59 +/- 2 mV (n = 10) within 40 s. Ouabain invariably depolarized PDbl. During both, sustained cooling or application of ouabain, the sensitivity of PDbl to bath potassium concentration decreased in parallel to PDbl pointing to a gradual decrease of potassium conductance.(ABSTRACT TRUNCATED AT 250 WORDS)