Effect of sensitization on spontaneous and phosphatidylserine-induced histamine release and on cyclic AMP and GMP levels in isolated rat mast cells.

Sprague Dawley rats were sensitized with 20 microgram 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 found to be specific in so far as it was calcium dependent and theophylline-inhibited. The basal level of cyclic AMP in mast cells was significantly depressed by sensitization. There was a relationship between the cyclic AMP/cyclic GMP ratio and the degree of spontaneous, phosphatidylserine-induced and anaphylactic histamine release. The results suggest that 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 cyclic AMP/cyclic GMP ratio. The relationship between these two phenomena is discussed.