IgE-mediated activation of human heart in vitro

We used human cardiac tissue from the right atrial appendages of patients undergoing corrective heart surgery to study content and de novo synthesis of mediators in the human heart. Human heart tissue contained 1.7 +/- 0.1 micrograms/g wet weight of histamine (mean +/- S.E.M.) and spontaneously produced 6-keto-PGF1 alpha (38.4 ng/g wet weight/min), PGF1 alpha (1.9 ng/g wet weight/min), PGE (1.7 ng/g wet weight/min) and thromboxane B2 (TxB2) (1.7 ng/g wet weight/min). Spontaneous release of PGD2, leukotriene C4 and histamine was negligible. Rabbit anti-human IgE (1-10 micrograms/ml) dose-dependently induced the release of histamine (5 to 15% of the total histamine content) and of PGD2 (5 to 100 ng/g of wet tissue). The effect of anti-IgE was dose-related and reached a maximum after 30-45 min of incubation. A significant linear correlation (rs = 0.90; p less than 0.001) was found between de novo synthesis of PGD2 and the secretion of histamine induced by anti-IgE challenge of human heart. These results support the concept that PGI2 is the main, but not the sole, product of arachidonic acid metabolism synthesized by human heart in vitro. Additionally, anti-IgE challenge of human heart in vitro induces the release of histamine and PGD2. The local concentrations of these mediators appear high enough to play some role in the modulation of several cardiac functions in vivo.