Effects of palmitate on the metabolism of leukocytes from guinea pig exudate

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SUMMARY The metabolism of palmitate by polymorphonuclear leukocytes (PMN) from guinea pig exudate in the presence of physiological concentrations of human serum albumin has been studied. The data indicate that with increasing concentration of palmitate in the medium (over a range of 0.54 to 5.4 pmoles/ml), there is a concomitant increase in uptake of oxygen and palmitate. The RQ decreased from 1.34 to 0.82 when palmitate was added to PMN (initial concentration: 3.8 pmoles/ml). A comparison was made between the effect of palmitate, and the effect of phagocytosis of polystyrene particles, on leukocyte respiration. The effect of palmitate was found to be additive to the effect due to phagocytosis when the latter occurred maximally, suggesting that the effect of palmitate on oxygen uptake was probably not due to phagocykosis of a high molecular weight palmitate-albumin complex. Palmitate uptake and the stimulation of oxygen uptake by palmitate were markedly inhibited by the glycolytic inhibitors sodium fluoride and iodoacetic acid. Cyanide and dinitrophenol had no effect on palmitate uptake or on the stimulation of oxygen uptake by palmitate. Palmitate uptake was the same in the presence and absence of glucose in the medium or under aerobic and anaerobic conditions. Glucose caused a 39% inhibition of the oxygen uptake of cells incubated in the absence of palmitate (Crabtree effect), whereas in the presence of palmitate, where there was a marked increase in oxygen uptake, no Crabtree effect was noted. Guinea pig monocytes (ME) were found to be more active metabolically than PMN. Oxygen and glucose uptake were seven times greater and palmitate uptake four times greater in MN as compared to PMN. With the addition of palmitate, only PMN showed a significant increase in oxygen uptake although the absolute increments in O2 uptake were the same for PMN and MN. Palmitate had no significant effect on the oxygen uptake of guinea pig circulating blood leukocytes and no net palmitate uptake was observed with such cells.