Table 2.

Membrane potential changes (± s.e.m.) following NH₄⁺ addition and withdrawal under different conditions

Condition	ΔEm upon NH4+ addition (mV)	ΔEm upon NH4+ withdrawal (mV)	Difference (mV)	Significance
Cl−-containing	18.3 ± 1.0	−17.0 ± 0.8	1.3 ± 1.3	P > 0.05 (N/S)
Cl−-free	20.8 ± 1.3	−20.6 ± 1.2	0.2 ± 1.8	P > 0.05 (N/S)
Cl−-containing with 10 μm CTZ & 10 μm bumetanide	20.5 ± 2.2	−15.5 ± 2.2	5.0 ± 3.1	P > 0.05 (N/S)
Cl−-containing with 10 μM ouabain	22.2 ± 1.3	−16.2 ± 1.5 (n = 12)	6.0 ± 2.0	P < 0.01 (S)

The table shows mean changes in E_m, ΔE_m (± s.e.m., n = 18 unless stated otherwise) upon NH₄⁺ addition and withdrawal under a variety of conditions. All solutions contained 40 mm NH₄⁺, and all NH₄⁺ exposures were approximately 100 min. The column designated 'Difference' shows the difference between the magnitude of ΔE_m upon addition of NH₄⁺ and upon its subsequent withdrawal. The column designated 'Significance' shows the result of an unpaired two-tailed t test to assess the significance or otherwise of this difference. N/S represents not significant and S represents significant.