Changes of intracellular electrolyte contents in rat skeletal muscle during body suspension

The CNS-mediated inhibition of active Na(+)-K+ transport in both "type S" muscle, soleus (SOL), and "type FF" muscle, extensor digitorum longus (EDL) was investigated in rats suspended horizontally. Plasma Na+ and K+ contents did not change during the suspension period. The relative wet weight of SOL decreased more than that of EDL by suspension. There was significant intracellular Na+ accumulation and K+ loss in both SOL and diaphragm of suspended rats. However, cerebrum, cerebellum, medulla oblongate, ventricle, liver, pancreas, kidney, intestine, aorta and EDL were spared from the intracellular Na+ accumulation and K+ loss. Sciatic nerve sectioning or cervical spinal cord transection recovered the Na+ and K+ contents in the SOL of suspended rats. The results indicate the existence of neural inhibition of the active Na(+)-K+ transport in skeletal muscle of the suspended rats.