Abstract
Sprague Dawley rats were sensitized with 20 .mu.g or 100 mg egg albumin (using pertussis vaccine as adjuvant). Mast cells isolated from the former group of animals showed a higher degree of histamine release upon challenge in vitro with egg albumin than those from the latter group. Using the lower amount of antigen for immunization mast cells from Hooded Lister rats showed an even higher degree of histamine release induced by antigen. An increased antigen-induced histamine release was associated with an increased spontaneous and phosphatidylserine-induced histamine release. Histamine release induced by phosphatidylserine was specific in so far as it was Ca dependent and theophylline-inhibited. The basal level of cyclic[c] AMP in mast cells was significantly depressed by sensitization. There was a relationship between the cAMP/GMP ratio and the degree of spontaneous, phosphatidylserine-induced and anaphylactic histamine release. Sensitization induces an increased release of histamine not only to the specific antigenic stimulus but also to more unspecific stimuli. Concomitantly there is a fall in the cAMP/cGMP ratio. The relationship between these 2 phenomena is discussed.