A study has been made of the exudate provoked by intrapleural carrageenan in rats. Various parameters have been measured including volume of exudate, numbers and types of cells. Pharmacological assay has shown the early release of histamine and 5HT into the exudate followed at later times by a release of prostaglandins, and a second release of histamine. The role of complement has been studied. Intrapleural injection of carrageenan after complement depletion produced a reduced migration of polymorphonuclear cells and also a reduction in volume of exudate. Prostaglandins remained unaffected by this treatment.

A model of reverse passive Arthus (RPA) reaction in the pleural cavity of rats is described. The time course of development of exudate and migration of cells has been examined. It has been found to be complement dependent and dominated by polymorphonuclear cells. The reaction reaches a peak around 6 hours after challenge. Cyclic AMP levels have been measured both intracellularly and extracellularly and have been found to persist at high levels after the waning of the reaction.

A model is described of acute inflammation in the pleural cavity of rats using calcium pyrophosphate as the irritant. This model would seem to simulate the pseudogout syndrome. It has been shown to be acute in onset, dominated by polymorphonuclear cells, complement independent. The advantage of the model is that volume of exudate, numbers and types of cells may be quantitated. Prostaglandins and cyclic AMP have been measured in the migrating cells. The significance of these findings has been discussed.