Pentoxifylline does not prevent endotoxin induced lung and liver lipid peroxidation in the adult sheep

Our purpose was to determine the effect of pentoxifylline pretreatment on endotoxin-induced (5 microgram/kg) lung and systemic oxidant activity, measured as lipid peroxidation. We used the awake adult sheep with lung and soft tissue lymph fistulae to monitor microvascular changes as well as to monitor oxygen delivery and consumption. Oxidant activity was monitored using the level of plasma conjugated dienes, a measure of circulating lipid peroxides, and lung and liver malondialdehyde content, a measure of tissue lipid peroxidation. Sixteen sheep were given endotoxin, eight of which were pretreated with pentoxifylline (20 mg/kg bolus) followed by a 6 mg/kg/hr infusion. We found that the degree of early endotoxin-induced pulmonary hypertension and hypoxia and later increased pulmonary microvascular permeability was not attenuated with pentoxifylline. In addition, a comparable increase in circulating conjugated dienes, lung neutrophil sequestration, and a three-fold increase in lung malondialdehyde was seen in both groups. Soft tissue QL also increased to the same degree in both groups. Liver MDA increased from a control of 110 +/- 20 nM/g tissue to 165 +/- 32 nM/g with endotoxin alone and to 260 +/- 55 nM/g with pentoxifylline pretreatment, a significant increase over both control and endotoxin alone groups. Pentoxifylline, however, did improve hemodynamic stability, required significantly less fluid, and prevented the hyperdynamic state seen at 4-5 hr post endotoxin. We conclude that pentoxifylline attenuates the initial endotoxin-induced hemodynamic instability, and later hyperdynamic state. However, pentoxifylline pretreatment does not appear to prevent endotoxin-induced oxygen radical release in the unanesthetized sheep.