ATP from glycolysis is required for normal sodium homeostasis in resting fast-twitch rodent skeletal muscle.

Myocellular sodium homeostasis is commonly disrupted during critical illness for unknown reasons. Recent data suggest that changes in intracellular sodium content and the amount of ATP provided by glycolysis are closely related. The role of glycolysis and oxidative phosphorylation in providing fuel to the Na(+)-K(+) pump was investigated in resting rat extensor digitorum longus muscles incubated at 30 degrees C for 1 h. Oxidative inhibition with carbonyl cyanide m-chlorophenylhydrazone, known as CCCP (0.2 microM), or by hypooxygenation did not alter myocellular sodium or potassium content ([Na(+)](i), [K(+)](i), respectively), whereas treatment with iodoacetic acid (0.3 mM), which effectively blocked glycolysis, dramatically increased [Na(+)](i) and the [Na(+)](i)/[K(+)](i) ratio. Experiments using ouabain and measurements of myocellular high-energy phosphates indicate that Na(+)-K(+)-ATPase activity is only impaired when glycolysis is inhibited. The data suggest that normal glycolysis is required to regulate intracellular sodium in fast-twitch skeletal muscles, because it is the predominant source of the fuel for the Na(+)-K(+)-ATPase.

Starvation enhances hepatic free radical release following endotoxemia.

Although it is well known that malnourished patients who become septic have an increased risk of organ failure and death compared to normally nourished individuals, the pathological processe(s) underlying this observation are unknown. To evaluate one possible explanation for this finding, we tested the hypothesis that malnutrition depresses hepatic antioxidant stores and accelerates hepatic release of oxygen free radicals in an animal model of sepsis. Male rats were either fasted (n = 14) or fed (n = 14) for 3 days prior to receiving lipopolysaccharide (LPS, 17 mg/kg intraperitoneally). Animals were weighed daily and then sacrificed 6 and 24 hr after LPS administration to determine hepatic superoxide anion (an oxygen free radical) release and liver glutathione (GSH, an antioxidant) content. Fasted rats were severely malnourished as indicated by a 23% decrease in body weight compared to fed rats, which gained 11% (P < 0.05). Liver GSH was depressed by 30% (P < 0.05) and 20% (P = 0.066) in the fasted compared to fed animals 6 and 24 hr after LPS administration. In addition, hepatic superoxide anion release was 210 and 75% higher in the fasted animals 6 and 24 hr after LPS injection (P < 0.05 at both time points). Liver superoxide anion release and GSH content were negatively correlated (P < 0.001, R = - 0.73) indicating that superoxide anion release increased as GSH content fell. Malnutrition leads to depletion of liver antioxidant stores with accelerated release of hepatic oxygen free radicals. Oxidant-mediated organ damage may be one cause of increased morbidity and mortality in malnourished, systemically infected patients.

The effects of dipyridamole and indomethacin on methotrexate cytotoxicity in LoVo human colon cancer cells.

Dipyridamole and indomethacin were studied for their effects in the in-vitro response of LoVo colon cancer cells to methotrexate (MTX) using a dye elution method. Dipyridamole 0.5-5 micrograms mL-1 or indomethacin 1 microgram mL-1 alone had little or no effect on cell growth. The tumour cells were refractory to even high concentrations of MTX (2.5-10 micrograms mL-1) alone or with indomethacin 1 microgram mL-1. In contrast, dipyridamole 0.5-5 micrograms mL-1 sensitized the cells to MTX 5 micrograms mL-1 (their growth was reduced by 25 to 69%), possibly by inhibiting thymidine salvage.