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Am J Physiol Cell Physiol 268: C1467-C1473, 1995;
0363-6143/95 $5.00
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AJP - Cell Physiology, Vol 268, Issue 6 C1467-C1473, Copyright © 1995 by American Physiological Society

ARTICLES

NAD-dependent 11 beta-hydroxysteroid dehydrogenase in cultured human colonic epithelial cells

W. B. Reeves
Division of Nephrology, University of Arkansas College of Medicine, Little Rock 72205, USA.

The inactivation of physiological glucocorticoids by 11 beta-hydroxysteroid dehydrogenase (11 beta-HSD) confers mineralocorticoid specificity to certain aldosterone target tissues. However, 11 beta-HSD activity in a human mineralocorticoid-responsive tissue has never been characterized. The present studies describe the features of 11 beta-HSD in the cultured human colonic epithelial cell line, T84. The 11 beta-HSD activity of T84 cells resided in the microsomal fraction and showed a marked preference for NAD rather than NADP as cofactor. NAD or NADP (200 microM) increased the conversion of corticosterone to 11-dehydrocorticosterone by 24.1 +/- 2.1 and 0.5 +/- 0.7 pmol.mg protein-1.20 min-1, respectively, indicating a > 40-fold preference for NAD vs. NADP. The Michaelis constant values for corticosterone and cortisol were 11.3 +/- 1.5 and 79.8 +/- 10 nM, respectively. The T84 11 beta-HSD was inhibited by 11-dehydrocorticosterone in a noncompetitive fashion [inhibition constant (Ki) = 180 +/- 9.6 nM] and by carbenoxolone in a competitive fashion (Ki = 17.4 +/- 1.3 nM). The expression of mineralocorticoid receptors in these cells was demonstrated by reverse transcriptase-polymerase chain reaction of mRNA isolated from T84 cells and by [3H]aldosterone binding studies. The coexpression of this NAD-dependent isoform of 11 beta-HSD and mineralocorticoid receptors is consistent with the view that the NAD-dependent isoform is responsible for the specificity of mineralocorticoid responses.


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B. Vogt, B. Dick, H.-P. Marti, F. J. Frey, and B. M. Frey
Reduced 11{beta}-hydroxysteroid dehydrogenase activity in experimental nephrotic syndrome
Nephrol. Dial. Transplant., May 1, 2002; 17(5): 753 - 758.
[Abstract] [Full Text] [PDF]


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