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Biochemical Localization of Aryl Hydrocarbon Hydroxylase in the Intestinal Epithelium of the Rat¹

Department of Experimental Therapeutics, Grace Cancer Drug Center, Roswell Park Memorial Institute, New York State Department of Health, Buffalo, New York 14263

The distribution of the carcinogen-metabolizing enzyme system, aryl hydrocarbon hydroxylase (AHH), was biochemically determined in the intestinal epithelium of the rat. A method of epithelial cell isolation in which fractions of cells are sequentially collected as a villus tip-to-crypt gradient was used. AHH activity was highest in the midvillus region, 40% lower at the villus tip, and practically nonexistent in the crypt region where active cell proliferation takes place. This distribution differed from those of sucrase and alkaline phosphatase (used here as markers for cellular differentiation), which were characteristically lowest in activity at the crypts and increased continuously to the villus tips. Conceivably, the midvillus peak of AHH activity may serve to protect or enhance the susceptibility of cells undergoing cell division in the nearby crypt regions, depending on whether the predominant function of AHH in the intestinal epithelium involves detoxication or activation of polyaromatic carcinogens.

¹ This investigation was supported, in part, by Grants CA-24538, CA-25362, and CA-22153 from the National Cancer Institute, Department of Health, Education and Welfare, and by Grant CTR-1253 from the Council for Tobacco Research.

² To whom requests for reprints should be addressed.

³ Present address: Medical Department, Norwich-Eaton Pharmaceutical, Norwich, N. Y. 13815.

⁴ The abbreviations used are: AHH, aryl hydrocarbon hydroxylase; BP, benzo(a)pyrene.

Received 8/24/81. Accepted 1/ 7/82.