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7<br />

<strong>Structure</strong>—Function Relationships in Hydroxysteroid Dehydrogenases<br />

Igor Tsigelny and Michael E. Baker<br />

University of California, San Diego, La Jolla, California<br />

I. Introduction<br />

Page 191<br />

Steroid hormones regulate a multitude of physiological processes in humans. Androgens and estrogens<br />

regulate sexual development and reproduction; glucocorticoids are important in the response to stress;<br />

vitamin D is important in bone growth; progestins are important for a viable fetus during pregnancy;<br />

mineralocorticoids regulate sodium and potassium balance to maintain normal blood pressure.<br />

Moreover, the growth of some breast and prostate tumors depends on steroids. With this multitude of<br />

medically important steroid-dependent actions, much research has gone into understanding their mode<br />

of action, with most of the effort concerned with the receptors that mediate the actions of steriods.<br />

A. High Blood Pressure and 11β-Hydroxysteroid Dehydrogenase<br />

It is only in the last decade that the role of hydroxysteroid dehydrogenases (Figure 1) in regulating the<br />

actions of steroids has been appreciated [1–6]. This mechanism for regulating steroid hormone action<br />

was uncovered in several laboratories studying various aspects of high blood pressure. One source was<br />

the study in the 1970s that identified the syndrome, Apparent Mineralocorticoid Excess (AME), a<br />

genetic disease that results in high blood pressure in children [7–10]. Also important is the work from<br />

laboratories investigating paradoxes in the mechanism of action of aldosterone in the kidney [1–4,9,10].<br />

These studies identified 11β-hydroxysteroid dehydrogenase (11β-HSD) as a key enzyme.<br />

http://legacy.netlibrary.com/nlreader/nlReader.dll?bookid=12640&filename=Page_191.html [4/5/2004 5:04:54 PM]

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