Figure 3.

Reduction or removal of extracellular Ca²⁺ does not affect the basolateral ATP-stimulated inhibition of NaCl absorption in isolated perfused mouse mTAL. (A) Representative original trace of the basolateral ATP effect in mouse mTAL during the reduction of basolateral extracellular Ca²⁺ to 100 nM. Recording of the electrical parameters V_te (transepithelial voltage) and ΔV₀ (voltage deflection) in freshly dissected and perfused mouse mTAL used to quantify transport changes. Note the slight reduction of V_te and ΔV₀ after reducing extracellular Ca²⁺ from 1.3 mM to 100 nM. (B–D) Summary of the transepithelial voltages (V_te), the transepithelial resistances (R_te) and the calculated equivalent short-circuit current (I'_sc) before, during (after 1 min) and after ATP wash-out (2 min after). (n = 4, ^*p < 0.05 by student's T-test). (E) Representative original trace of the basolateral ATP effect in mouse mTAL during the removal of basolateral extracellular Ca²⁺ (5 mM EGTA). Note the continuous reduction of V_te and ΔV₀ after removing extracellular Ca²⁺. (F,G) Summary of the V_te and R_te before, during (after 1 min) and after ATP wash-out (2 min after). (n = 4, ^*p < 0.05 by student's T-test). Note the artificially low R_te values in (G), especially during application of bl. ATP.