Table III.

Effects of 10⁻⁶ M salbutamol and 10⁻³ M ouabain on ⁸⁶Rb uptake and intracellular Na⁺ content in soleus muscles from WT and mutant mice

Genotype	86Rb uptake	P-value	Intracellular Na+ content	P-value
	nmol/g wet wt/min		µmol/g wet wt
WT	652 ± 66 (6)	<0.02	7.4 ± 0.4 (6)	<0.001
WT + salbutamol	883 ± 45 (6)		4.5 ± 0.2 (6)
WT + ouabain	186 ± 9 (5)	<0.002	30.9 ± 0.5 (5)	>0.3
WT + ouabain + salbutamol	252 ± 12 (6)		32.0 ± 1.0 (4)
Mutant	1,005 ± 39 (6)	<0.005	11.7 ± 1.0 (6)	<0.005
Mutant + salbutamol	1,198 ± 34 (6)		6.6 ± 0.6 (6)
Mutant + ouabain	154 ± 7 (4)	<0.005	46.8 ± 1.2 (4)	>0.15
Mutant + ouabain + salbutamol	207 ± 10 (6)		48.6 ± 0.6 (6)

The muscles were mounted at resting length and equilibrated for 30 min at 30°C in KR buffer. Then, the muscles were incubated at rest for 10 min in buffer containing 0.2 µCi/ml ⁸⁶Rb with or without salbutamol, washed four times for 15 min in ice-cold Na⁺-free Tris-sucrose buffer during gassing with air, blotted, weighed, and taken for flame photometry and counting. ⁸⁶Rb uptake was calculated on the basis of the specific activity of the isotope in the buffer (see Materials and methods), and the results are expressed in nanomoles/gram of wet weight/minute. The ouabain-suppressible component of ⁸⁶Rb uptake was determined by deducting the uptake of ⁸⁶Rb measured in muscles preexposed to 10⁻³ M ouabain for 10 min before the incubation with ⁸⁶Rb.