Rapid histamine assays: a method and some theoretical considerations.

1. An automatic method for doing assays on superfused isolated tissues has been developed using the Autoanalyser sample turntable.2. Responses in the range used for assays are independent of the preceding responses when elicited at 1 min intervals. A longer interval was found to be necessary when using the conventional immersion method.3. The index of precision was similar to that reported for other superfusion methods.4. The assay method behaved as though it were assaying histamine selectively in two samples of material released by the anaphylactic reaction of passively sensitized guinea-pig lung. Responses to anaphylactically released material were also independent of the preceding response at 1 min intervals.5. Some theoretical considerations are discussed concerning the arrangement of doses, and the interpolation of results, in 2 + 1 dose assays. The object was to maximize speed while still allowing a valid estimate of the potency and its error.