Table 1. Medium acidification by ammonia uptake of oocytes expressing AQP1 wild-type and mutants.

Acidification rate	AQP1	HA	RV	HA/RV	HA/FA
JH+ [10-10 mol H+ s-1 oocyte-1]	0.41 ± 0.035 (5)	0.70 ± 0.03 (4)	0.58 ± 0.08 (5)	1.6 ± 0.07 (4)	0.56 ± 0.03 (5)
		P < 0.003	P < 0.003	P < 0.0005	P < 0.008

Oocytes were transferred into weakly buffered medium containing 20 mM NH₄Cl. The initial rate of acidification of the bathing solution (J_H⁺) is indicated. (±SEM; n is given in parentheses). Uninjected controls were as AQP1-expressing oocytes.