عنوان

Characterization of intestinal N-acetyltransferases

TLpq304275070

انگلیسی

Characterization of intestinal N-acetyltransferases

[Thesis]

J. A. Ware

C. K. Svensson

Wayne State University

1996

155

Ph.D.

Wayne State University

1996

Experimental and clinical evidence indicates that AcCoA:arylamine N-acetyltransferases (NATs) are involved in the bioactivation and inactivation of a wide variety of arylamine, hydrazine and carcinogenic arylamine xenobiotics. In this project, we report the intestinal longitudinal distribution of NATs in the hamster, mouse and two strains of rat utilizing the model arylamine substrates procainamide (PA) and p-aminobenzoic acid (PABA) for the monomorphic (NAT1) and polymorphic (NAT2) in the rodent, varies for each species examined and between strains of rat. In particular, NAT1 and NAT2 in the F-344 rat is constant from proximal to distal intestine. NAT1 and NAT2 for the WKY rat are significantly higher in the large intestine than small intestine. The distribution of NAT1 and NAT2 in the syrian golden hamster decreases 4-fold from proximal to distal intestine. The Swiss albino mouse has detectable NAT1 activity in the small intestine while the large intestine is below limits of detection. NAT2 activity, however is highest in the cecum followed by proximal small intestine, colon and ileum. Although these substrates have been shown to be selective for NATs, they are not specific. Therefore, a series of biochemical studies were undertaken to evaluate NAT multiplicity in the intestine of the F-344 rat. To assess multiplicity of NAT expression, selective inhibition, differential sensitivity to heat inactivation and kinetic analysis were performed on intestinal cytosol. Eadie-Hofstee transformation of PA N-acetylation yielded a curvilinear plot indicative that a low affinity-high capacity enzyme aside from NAT1 (presumably NAT2) was contributing PA N-acetylation activity. PA activity was found to exhibit approximately 4- to 5-fold greater thermostability than PABA activity. Furthermore, PA acetylation could be selectively inhibited with vinyl fluorenyl ketone (2.5-5 muM) but not methotrexate (up to 2 mM). Taken together, these studies suggest the expression of both NAT1 and NAT2 in the intestine of the F-344 rat. Studies to determine the cellular localization of NAT within the crypt to villus axis suggest that both NAT1 and NAT2 are heterogeneously expressed in the crypt to villus tip enriched cell populations, with highest N-acetylation activity resided in the villus tips.

arylamine

Biological sciences

Health and environmental sciences

hydrazine

NAT

Pure sciences

C. K. Svensson

J. A. Ware

p

[Thesis]

276903

a

Y