TABLE 3.

The effect of ouabain on the Na/K-ATPase activity and NHE3 activity in RPT primary cultures derived from the R and S rats

RPTs were isolated from the R and S rats fed with low salt (0.3% NaCl) diet and cultured as described under “Materials and Methods.” After ouabain treatment, cells were washed three times with ice-cold 1× PBS before isolation of crude heavy membrane fractions and BBMVs. The Na/K-ATPase enzymatic activity in crude heavy membrane fractions was expressed as μmol/mg protein/hour from four independent experiments (each performed in triplicate). NHE3 activity (²²Na⁺ uptake) in BBMVs was expressed as relative values (% of control as 100%) from four independent experiments (each performed in triplicate). **, p < 0.01 compared to control.

	Strain	Control	Ouabain
			10 μmol/liter, 1h
Na/K-ATPase activity	R	61.2 ± 3.6 (n = 4)	46.8 ± 3.5** (n = 4)
	S	60.8 ± 4.1 (n = 4)	57.9 ± 4.5 (n = 4)
NHE3 activity (%)	R	100 ± 5.2 (n = 4)	71.2 ± 5.5** (n = 4)
	S	100 ± 6.1 (n = 4)	96.4 ± 6.5 (n = 4)