| Abstract: | Purified histamine-sensitizing factor (HSF) of Bordetella pertussis induced in vitro an alteration in the pharmacologic response of rat atria to acetylcholine. Spontaneously beating atrial preparations isolated from rats were exposed to HSF at a concentration of 50 ng/ml at 37 C for 30 min to 4 hr and washed with Krebs-Ringer solution, and then tested at 1-hr intervals up to 28 hr during incubation for their responses to epinephrine and acetylcholine. At 13 hr after exposure to HSF, irrespective of the exposure period, the HSF-treated atria, in which positive-inotropic action of epinephrine was manifested, depressed the negative-inotropic response to acetylcholine. The activity of HSF was neutralized by anti-HSF serum only in the first 3 hr of exposure. Only 1.8% of the added 125I-labeled HSF bound “specifically” to one pair of atria for the manifestation of the altered response. |
