Table 1.

Effects of 300 μm ATP on Cl⁻ transport across the apical membranes

	aCl1			F/Fo
	Control (mm)	ATP (mm)	Difference (mm)	Control (10−3 s−1)	ATP (10−3 s−1)	Difference (10−3 s−1)
A. Nucleotide added to the apical side only
Apical ATP (n = 8)
Cl → NO3	−0.4 ± 0.3	−7.5 ± 1.5	−7.1 ± 1.6****	0.02 ± 0.01	0.51 ± 0.13	0.49 ± 0.14***
NO3→Cl	+0.5 ± 0.3	+9.0 ± 1.9	+8.5 ± 1.9*****	0.02 ± 0.01	0.60 ± 0.15	0.58 ± 0.15***
B. Nucleotide applied first to the basolateral side then to the apical side
Basolateral ATP (n = 5)
Cl→NO3	−1.4 ± 0.2	−4.8 ± 1.1	−3.4 ± 1.0****	0.20 ± 0.12	0.40 ± 0.13	0.20 ± 0.14n.s.
NO3→Cl	+2.2 ± 0.5	+5.2 ± 1.1	+3.0 ± 1.1****	0.18 ± 0.04	0.37 ± 0.13	0.19 ± 0.15*
Apical ATP (n = 5)
Cl→NO3	−1.4 ± 0.2	−7.0 ± 1.8	−5.6 ± 1.6****	0.20 ± 0.12	0.71 ± 0.23	0.51 ± 0.15**
NO3→Cl	+2.2 ± 0.5	+7.2 ± 1.9	5.0 ± 1.8****	0.18 ± 0.04	0.48 ± 0.13	0.30 ± 0.18**

[Cl⁻]_i changes and the rates of chloride transport (F/F_o, 10⁻³ s⁻¹) were followed when perfusing the apical side of the A6 cell monolayer with Cl⁻−containing Ringer solution being replaced by NO⁻₃−containing Ringer solution (Cl→NO₃) or vice versa (NO₃→Cl). ATP was added to the solution bathing the apical side of the A6 cell monolayer 1 min before chloride substitution (A). In B, the ATP effect was followed when adding the nucleotide to the basolateral side then to the apical side (see Fig. 3B). Significance levels: n. s., not significant

^*P < 0.1

^**P < 0.05

^***P < 0.010

^****P < 0.005.