Use of plasma histamine levels to monitor cutaneous mast cell degranulation.

A simple, minimally invasive procedure for monitoring cutaneous mast cell degranulation in vivo in man is described. Plasma histamine levels in venous blood draining the site of intradermal histamine, morphine, and antigen challenges were determined with a modified radioenzymatic assay. Elevations in plasma histamine above baseline levels of 0 to 0.6 ng/ml were measured after intradermal histamine; levels of 1.4 to 85.2 ng/ml were obtained after a 2 microgram intradermal challenge in 16 subjects. After antigen testing, peak plasma histamine levels ranged from 1.1 to 24.4 ng/ml (n = 9), and after morphine sulfate skin testing peak plasma histamine levels ranged from 2.3 to 12.7 ng/ml (n = 4). The time to achieve peak plasma histamine levels ranged from 2 to 10 minutes after histamine, from 5 to 15 minutes after antigen, and from 1 to 8 minutes after morphine challenges. Plasma levels returned to baseline within 30 minutes after histamine and morphine challenges but took more than 60 minutes for antigen challenges. With careful choice of the skin test site in relation to venous drainage, plasma histamine increases after either histamine or antigen were reproducible and reliable. Plasma histamine levels peaked 5 to 10 minutes before maximal development of the wheal-and-flare responses after histamine, antigen, or morphine skin tests. The wheal-and-flare skin tests continued to increase in magnitude despite rapidly declining plasma histamine levels. Thus skin tests eliciting reactions ordinarily seen in an allergist's office cause measurable increases in plasma histamine levels that can be used to directly monitor mast cell degranulation in man in vivo.(ABSTRACT TRUNCATED AT 250 WORDS)