Effect of endotoxic shock on basal and insulin-mediated Na+/K(+)-pump activity in rat soleus muscle

This study evaluated basal and insulin-mediated Na+/K+ transport in skeletal muscle during endotoxic shock. Fasted male Holtzman rats (80-100 g) were killed 5 hr after the i.v. injection of saline (control) or 20 mg/kg Salmonella enteritidis endotoxin. 86Rb+ uptake into the cellular compartment of soleus muscle was determined in the presence and absence of 100 mU/ml insulin. The rate coefficient and rate of 22Na+ efflux and muscle intracellular 22Na+ content (in percentage of total muscle 22Na+) were determined in the presence and absence of 1 mM ouabain. The rate of basal cellular 86Rb+ uptake (cpm x 10(3).g wet weight-1.min-1) was not significantly different between control (77.7 +/- 2.9) and endotoxic soleus muscles (76.1 +/- 3.9). Insulin increased the rate of cellular 86Rb+ uptake by 19% in control (92.4 +/- 3.7) and 23% in endotoxic soleus muscles (93.8 +/- 4.1). Cellular 22Na+ content was 40% greater in endotoxic muscle (16.8 +/- 1.4) as compared to control muscles (12.0 +/- 0.9). The rate coefficient for ouabain-sensitive 22Na+ efflux in endotoxic muscles (0.028 min-1) was 1.7-fold greater than that in control muscles (0.017 min-1). The rate of ouabain-sensitive 22Na+ efflux was more than doubled in endotoxic muscles (0.470%/min) compared with control muscles (0.204%/min). Endotoxic shock did not alter insulin's ability to stimulate Na+/K+ transport in muscle. An increase in the electrogenicity of the Na+/K+ pump is consistent with an increased rate coefficient for 22Na+ efflux, with no change in the rate of 86Rb+ uptake in endotoxic soleus muscle.(ABSTRACT TRUNCATED AT 250 WORDS)