Dissociation between prostaglandin and malondialdehyde formation in exudate and increased levels of malondialdehyde in plasma and liver during granulomatous inflammation in the rat.

During kaolin-induced granuloma pouch inflammation in the rat the concentration of malondialdehyde (MDA) in the exudate, measured by the 2-thiobarbiturate method, steadily increased and this increase was correlated with the increase in granuloma weight. There was a complete lack of correlation between the concentrations of MDA and prostaglandin (PG)-like material in the inflammatory exudate. Whereas the concentration of PGs reached a maximum 1 day after the induction of inflammation and returned to control levels on day 4, the MDA concentration continuously increased from the initiation of inflammation up to day 16. During granuloma development the concentration of MDA in the plasma reached a maximum on day 2 in parallel with the concentration in the liver, then both plasma and liver MDA decreased to levels observed in control rats. Between day 2 and 8 of the inflammatory process homogenates of livers from inflamed rats showed an increased formation of MDA on incubation, the amount formed being maximal on day 4. The results of the present study are discussed in view of a possible involvement of lipid peroxidation in inflammation.