Figure 1. Role of histidase in SC acidification.
(a) Histidase activity in the stratum corneum (SC) was measured in newborn rats and rats at age 4–5 days (n = 6). (b) The SC surface pH in Peruvian and matched controls was measured with a flat, glass surface electrode (Mettler-Toledo, Giessen, Germany), attached to a pH meter (Skin pH Meter PH 900; Courage & Khazaka, Cologne, Germany). HIS−/−, n = 8; HIS +/−, n = 14; wild type, n = 6.