Effect of endotoxic shock on skeletal muscle intracellular electrolytes and amino acid transport.

Soleus muscle intracellular electrolytes and alpha-aminoisobutyric acid (AIB) uptake and its regulation by insulin were investigated during endotoxic shock in vivo. Fasted rats (90 g) were injected with [14C]AIB (1-10 mg/kg, iv) and Salmonella enteritidis endotoxin (20 mg/kg, iv) or saline and killed 1-5 h later. AIB uptake into muscle was corrected for uptake into extracellular space (measured as insulin distribution in muscle in vivo) and expressed as [AIB]/[AIB] ratios to assess active transport. The maximum level of active AIB cell transport by extracellular endotoxic muscles [3.3 +/- 0.2 (SE)] was lower than control muscles (4.9 +/- 0.3) at the time when plasma insulin concentration in endotoxic rats (16.8 +/- 2.0 uU/ml) was greater than controls (7.9 +/- 1.7 uU/ml). Insulin-stimulated AIB transport was significantly lower in endotoxic muscles (from a basal value of 3.3 +/- 0.2 to 4.4 +/- 0.5, 5.0 +/- 0.3, and 4.9 +/- 0.3 at 125, 250, and 500 mU/kg intravenous insulin, respectively) than in control muscles (from 4.9 +/- 0.3 to 5.7 +/- 0.2, 8.0 +/- 0.4, and 10.8 +/- 0.8). The intracellular electrolyte concentrations in endotoxic soleus muscles ([Na] = 15.87 +/- 0.9, [K] = 145 +/- 1.7, [Cl] = 14.61 +/- 0.9) were substantially altered when compared with control muscles ([Na] = 9.33 +/- 1.1, [K] = 164 +/- 1.5, [Cl] = 4.1 +/- 0.6) 5 h postinjection. The membrane potential, estimated from chloride equilibrium potential was lower in endotoxic muscles (-52.7 +/- 1.6 mV) when compared with control muscles (-89 +/- 3.5 mV).(ABSTRACT TRUNCATED AT 250 WORDS)