Measurement of chloride movement across single proximal tubules of Necturus kidney

¹ Department of Physiology, Cornell University Medical College, New York City

To study the relationship between chloride fluxes and electrochemical potential difference, single proximal tubules of Necturus were perfused with a modified Ringer's solution containing Cl³⁶. Collected fluid samples were assayed for radioactivity of inulin-C¹⁴ carboxylic acid and of Cl³⁶, and chloride concentration was measured by electrometric titration. No significant concentration gradient for chloride was observed while inulin concentration ratios significantly above unity indicated fluid reabsorption. The results indicate that net reabsorptive chloride movement represents only a small fraction of chloride efflux. The relationship between chloride outflux/influx ratio and transtubular electrochemical potential difference is tentatively interpreted as indicating that reabsorptive chloride movement is passive in nature.