The analysis of arachidonic acid metabolites in normal, uninvolved and lesional psoriatic skin.

Collection of exudate from suction bullae is a commonly used method for sampling human skin for mediator analysis. It is satisfactory on skin of normal structure but is unreliable on lesional psoriatic skin in which there are major structural changes and excessive scaling. Collection of exudates from abraded sites was found to be a suitable alternative method for psoriatic skin. Arachidonic acid and 12-HETE, but not PGE2, were significantly higher in exudate from abraded lesional psoriatic skin (494 +/- 88, 45.9 +/- 4.2 and 9.6 +/- 1.8 ng/ml respectively, mean +/- sem, n = 5) compared to uninvolved skin (154 + 38, 18.5 + 5.1 and 7.7 + 1.9 ng/ml) or skin of normal volunteers (119 +/- 37, 14.5 +/- 6.7 and 4.5 +/- 1.6 ng/ml, n = 7) which were similar. The coefficient of variation for exudate collection and mediator analysis was usually less than 55%. The analysis of lipoxygenase and cyclooxygenase products was simplified by the use of chlorobutane to extract preferentially arachidonic acid and HETEs from neutral aqueous solutions.