Chronobiological study of plasma exudation in carrageenan-paw oedema in the rat

The time-courses of exudation of protein-bound Evans' blue and of the formation of oedema following the injection of carrageenan (2 mg) or normal saline in the rat hind paw at 10.00 hours and 21.00 hours were studied. During the first 90 min after the carrageenan injection, the tissue content of the dye and the oedema formed were much greater when the inflammatory agent was administered at 21.00 hours than at 10.00 hours. A second study carried out at every 3 hours of the 24 hour span showed the presence of a circadian rhythm in the exudation of protein in the paw and in the formation of oedema. The paw volume and content of the dye were found to be highest between 19.00 hours and 01.00 hours whereas the minimal values were obtained at 16.00 hours. There is a correlation between the exudation of plasma proteins and the formation of oedema.