Inhibition of d-tubocurarine-induced histamine release by halothane

To determine whether anesthetics modify mediator release, the authors measured the amount of histamine released by d-tubocurarine (dTC) in human foreskin preparations in the presence of high (2.0%) and low (0.5%) halothane concentrations and nitrous oxide (10%). Freshly excised human foreskins were divided into four matched pieces. Two matched pieces were aerated with oxygen, and the other two with an oxygen-anesthetic gas mixture. One chamber of each served as a control, while the other was stimulated with 3 X 10(-5) M d-tubocurarine for 30 min. Supernatant histamine concentrations were measured by automated fluorometry. Percent histamine release was determined by dividing the experimentally released histamine concentration by the total histamine released after the tissue was sonicated and boiled. Neither halothane nor N2O alone altered spontaneous histamine release. Histamine release by d-tubocurarine was significantly reduced by 2% halothane compared to d-tubocurarine alone (2.8% +/- 0.9 vs. 13.9% +/- 3.7, mean + SEM) (P less than 0.05) in the in vitro preparation. Histamine release was reduced in the preparations pretreated with 0.5% halothane group, but this was not statistically significant (P greater than 0.05) when compared to d-tubocurarine alone. N2O (10%) did not reduce d-tubocurarine-induced histamine release. The authors conclude that halothane, in clinically used concentrations, significantly impairs histamine release from human neonatal foreskin preparations.