The basis of the histamine assay in skin.

Abstract

1 The assay of wheal response to histamine injected sub-epidermally has been reviewed.Several discrepant claims were found in earlier work. 2 The saline control injection may evoke a wheal, which if present should be allowed for in the assay procedure. 3 There was no evidence for a limb dominance effect.4 Using a 3.26 mm (1 mg ml-1) standard solution of histamine acid phosphate (1.18 mm as free base) and 0.1 ml injections, the straight central portion of the assay curve was found to be between 0.3 and 2.3 x 10-3 mM, as free base, with an ED50 of about 0.018 mm histamine base.

Actions of terfenadine and cimetidine on histamine wheal formation.

“…In earlier work it was shown the histamine wheal growth begins after a delay of 1-2 min, and proceeds for up to 9-10 min from injection, growth occurring by piecemeal accretion of small territories, though at a general rate which accords with assisted diffusion in the skin from an initial area corresponding to that of the subepidermal injection bleb, i.e. about 41 mm2 [1,4]. In those analyses, data were fitted best by linear regression slopes.…”

“…Histamine tests were made between 11.00 h and 12.00 h in an air conditioned laboratory at 210 C + 1.5°C. The methods used have already been described in detail [1,4]; a solution of histamine acid phosphate in isotonic saline 1 mg ml-'1, was diluted to 1 in 4 and 1 in 16 to yield solutions equivalent to histamine free base, 0.3 mm and 0.074 mm. These were injected subepidermally, with a saline control in volumes of 0.1 ml of each, by tuberculin syringes with 25 gauge needles, into the palmar surface of the left forearm.…”

“…Areas were measured as the sum of complete graph squares plus half the sum of incomplete squares within each ring. Reasons for measuring area, not volume, of the wheals have been discussed before [4].…”

The basis of the histamine assay in human skin: II. Wheal formation.

“…Histamine solutions were injected (0.1 ml) subepidermally, with very fine needles, [1] into the palmar aspect of the forearm in the area between 4 and 12 cm below the elbow crease. Four concentrations of histamine acid phosphate in isotonic saline were used, 2.25, 0.56, 0.14, 0.035 mmol 1-1 calculated as histamine free base.…”

“…The histamine assay procedure depends usually upon fully developed wheals; in our first paper wheals were measured at 10 min from injection time [1]. During that work it was confirmed that wheals appeared after a delay [2] and that wheal growth in time rose slowly to the maximum.…”