Effects of the anion transport inhibitor, SITS, on the proximal straight tubule of the rabbit perfused in vitro.

Conventional microelectrodes were used to study the effects of SITS (4-acetamido-4'-isothiocyanostilbene-2,2'-disulfonate) on the basolateral membrane potential Vbl of the superficial proximal straight tubule (PST) of the rabbit kidney perfused in vitro. Addition of 0.1 mM SITS to the bathing solution resulted in a slow and irreversible hyperpolarization of Vbl from -42.5 +/- 1.17 (37) mV to -77.3 +/- 0.83 (52) mV. The new steady-state potential was reached in 10 to 15 min and was accompanied by visible cell swelling. Associated with this Vbl hyperpolarization was: 1) an increased steady-state depolarization (from 6.2 +/- 0.77 (17) mV to 25.7 +/- 0.83 (29) mV) in response to increasing bath potassium concentration from 5 to 16.7 mM (HK); 2) a decreased transient depolarization (from 19.8 +/- 1.88 (8) mV to 0.43 +/- 0.37 (8) mV) in response to decreasing bath bicarbonate concentration from 22 to 6.6 mM at constant bath pH (L-HCO3); and 3) inhibition of a depolarizing overshoot and a decreased steady-state depolarization (from 35.9 +/- 1.84 (12) mV to 4.7 +/- 1.37 (13) mV) in response to reducing bath sodium concentration from 144 to zero (0-Na). Sodium, chloride and NMDG (N-methyl-D-glucamine) were used as the substituting ions, respectively. These results are consistent with the presence of a coupled sodium-bicarbonate carrier in the basolateral membrane which is electrogenic and SITS inhibitable.(ABSTRACT TRUNCATED AT 250 WORDS)