LOCALIZATION AND INDUCTION OF CYTOCHROME-P450 1A1 AND ARYL-HYDROCARBON HYDROXYLASE-ACTIVITY IN RAT NASAL-MUCOSA

Cytochrome P450 1A1 was localized immunohistochemically and benzo[a]py rene hydroxylase activity was identified in situ by means of fluoresce nce histochemistry in the nasal mucosa of untreated, 3-methylcholanthr ene-treated or Aroclor 1254-treated rats. Cytochrome P450 1A1 was loca lized predominantly within Bowman's glands, with considerably less sta ining occurring in the olfactory epithelium of untreated rats. Similar ly, benzo[a]pyrene was hydroxylated to the greatest extent in Bowman's glands and, to a lesser extent, in olfactory epithelial cells. Pre-tr eatment of tissue sections of nasal mucosa with anti-P450 1A1 inhibite d most of the benzo[a]pyrene hydroxylase activity present. Although 3- methylcholanthrene treatment did not affect either cytohrome P450 1A1 or hydroxylase activity in the nasal mucosa, a single intraperitoneal injection of Aroclor 1254 significantly increased anti-P450 1A1 bindin g in Bowman's glands and in the olfactory and respiratory epithelia, a nd dramatically enhanced benzo[a]pyrene hydroxylase activity in the ep ithelia and the subepithelial ducts and glands in both the olfactory a nd respiratory regions. In contrast to its effects on cytochrome P450 1A1, Aroclor 1254 produced a considerably greater induction of hydroxy lase activity in the respiratory region, especially in the seromucous glands, than in the olfactory region. These results suggest that Arocl or 1254 treatment also induces other forms of cytochrome P450 in the r espiratory region of the nasal mucosa.