Transport characteristics of renal collecting tubules: influences of DOCA and diet.

Isolated renal cortical collecting tubules from rabbits were studied at random (control) and from rabbits maintained on diets containing either high or low Na and K content or injected with DOCA for up to 31 days. In general, the values of transepithelial voltage (VT) and electrical resistance (RT) varied considerably between tubules. When rabbits were fed a high K, low Na diet or were injected with DOCA the values of VT increased. Of interest was the observation that tubules obtained from rabbits maintained on DOCA for 11-18 days or longer possessed markedly elevated values of VT (mean VT, -54 mV) and a marked increase in their ability to reabsorb Na and secrete K at rates well above the levels observed even at 3-6 days of treatment when it was expected that maximal transport rates would have been achieved. From the estimates of the conductances of Na, K, and Cl, the data could be interpreted to mean that DOCA caused a decrease in the conductance of Cl, perhaps via the shunt pathway, while elevating the conductances of Na and K, thereby enhancing active Na and especially K transport by this nephron segment.