Characterization of rat 17 beta-hydroxysteroid dehydrogenase type 1 gene and mRNA transcripts.

In the present study, the gene encoding rat 17 beta-hydroxysteroid dehydrogenase type 1 (rHSD17B1 gene) was cloned and characterized. Like the analogous human gene (hHSD17B1), rHSD17B1 contains six exons and five introns spanning approximately 2.2 kb. The identity between the exons and introns of the two genes ranges from 58% to 82% and 42% to 57%, respectively. In contrast to hHSD17B1, rHSD17B1 is not duplicated. The cap site for rHSD17B1 was localized to position -41 upstream of the ATG translation initiation codon. Sequence comparison of the first 200 bp upstream of the cap site showed 72% identity between the human and rat HSD17B1 genes, including a conserved GC-rich area. Further upstream, no significant identity between the two genes was observed and several, cis-acting elements known to modulate the expression of hHSD17B1 are not conserved in the rat gene. Rat HSD17B1 unlike hHSD17B1 with two cap sites, possesses two polyadenylation signals, thus resulting in two mRNAs.

Expression of 17beta-hydroxysteroid dehydrogenase type 1 and type 2, P450 aromatase, and 20alpha-hydroxysteroid dehydrogenase enzymes in immature, mature, and pregnant rats.

In the present study, we evaluated the expression and regulation of 17beta-hydroxysteroid dehydrogenase (17HSD) type 1 and type 2, cytochrome P450 aromatase (P450arom), and 20alpha-hydroxysteroid dehydrogenase (20HSD) in mature and pregnant rats. Immunohistochemical analysis of rat 17HSD type 1 showed that the enzyme is exclusively expressed in the granulosa cells of developing, healthy, primary, secondary, and tertiary follicles at all stages of the estrous cycle and pregnancy, and is not detected in the corpora lutea. The data showed that the amount of the enzyme expressed in the follicle increases as follicular maturation progresses and is highest in tertiary and Graafian follicles. However, Northern blot analysis of total RNA from whole ovaries showed a rather constitutive expression of the 17HSD type 1 enzyme. It is evident that compared with P450arom, 17HSD type 1 is more widely expressed in the follicles during the various maturational stages of folliculogenesis. Hence, the data indicate distinct localization, expression, and regulation patterns for 17HSD type 1 and P450arom during the rat estrous cycle and pregnancy. Furthermore, compared with the two estradiol biosynthetic enzymes, a different expression pattern was detected for 20HSD messenger RNA. During the estrous cycle the enzyme was detected in the ovaries throughout the cycle, and in the ovaries of pregnant animals the enzyme showed an expression pattern the opposite of that observed for P450arom. Rat 17HSD type 2, not detected in the ovaries, was constitutively expressed in both female and male liver and small intestine in 21-day-old fetuses up to 6-week-old mature animals. Similarly, in these tissues the enzyme was constitutively expressed in normal cycling and pregnant animals, but it showed increasing expression in the placenta as pregnancy advanced. The relatively constitutive expression of the enzyme at all physiological stages of the animals suggests a general role for the enzyme in the inactivation of circulating sex steroids.

Cloning of rat 17 beta-hydroxysteroid dehydrogenase type 2 and characterization of tissue distribution and catalytic activity of rat type 1 and type 2 enzymes.

17 beta-Hydroxysteroid dehydrogenases (17HSDs) are enzymes catalyzing the conversion between 17 beta-hydroxy- and 17-ketosteroids. Both estrogens and androgens possess their highest activity in the 17 beta-hydroxy form, and the enzymes, therefore, regulate the biological activity of sex hormones. In this study, we have characterized the complementary DNA (cDNA) for rat 17HSD type 2. The cDNA encodes a protein with a predicted mol wt of 42,010 Da. The protein has 77% similarity and 62% identity with the human 17HSD type 2 enzyme. Furthermore, the hydropathicity profiles of the enzymes are very similar. The two isozymes contain a putative transmembrane region close to the N-terminus. However, the rat isozyme lacks the two lysine-rich amino acid cluster present at the N- and C-terminals of human 17HSD type 2. The tissue distribution of the rat 17HSD type 1 and type 2 enzymes is very similar to that of the human enzymes. The highest expression of 17HSD type 2 was detected in the placenta. In addition, a 1.5-kilobase messenger RNA for the enzyme was detected in the small intestine, liver, and kidney of both sexes. The two messenger RNAs for rat 17HSD type 1 (1.4 and 1.7 kilobases) were highly expressed only in the ovary, and at very low concentrations in the kidney of both sexes. Transiently expressed rat 17HSD type 2 showed oxidative activity almost exclusively in cultured human embryonic kidney 293 cells, converting estradiol into estrone and testosterone into androstenedione, whereas the opposite was observed for the rat type 1 enzyme. The data suggest that similarly to the corresponding human isoforms, rat 17HSD type 2 is mostly involved in the oxidation of 17 beta-hydroxysteroids into their relatively inactive keto derivative in peripheral tissues, whereas rat 17HSD type 1 is mainly involved in the glandular biosynthesis of estradiol.

Characterization of 17beta-hydroxysteroid dehydrogenase isoenzyme expression in benign and malignant human prostate.

In the present study, expressions of 17beta-hydroxysteroid dehydrogenase (17HSD) types 1, 2, and 3, 5alpha-reductase type 2 and human androgen receptor mRNAs were determined in 12 benign prostatic hyperplasia and 17 prostatic carcinoma specimens. 17HSD type 2 was found to be the principle isoenzyme expressed in the prostate. Significantly higher expressions of 17HSD type 2 and 5alpha-reductase type 2 were detected in benign prostatic hyperplasia compared with the carcinoma specimens. Expression of the androgen receptor in the 2 groups was not significantly different. 17HSD type 3 mRNA was not detected in any of the specimens investigated. Only low constructive expression of the 2.3 kb mRNA of 17HSD type 1 was seen. Immunohistochemical analysis indicated that this did not lead to significant enzyme expression, only faint staining for the enzyme protein being detected, mainly in uroepithelial cells. No significant correlation was found between any of the mRNAs analysed, but the data on 5alpha-reductase type 2 mRNA support the presence of an increased proportion of 5alpha-dihydrotesterone in the hyperplastic prostate. In cultured PC-3 prostatic cancer cells and in the transiently transfected human embryonic kidney 293 cells, 17HSD type 2 was found exclusively to convert 5alpha-dihydrotestosterone and testosterone into the less potent 17-keto compounds 5alpha-androstanedione and 4-androstenedione, respectively. We suggest that the 17HSD type 2 isoenzyme plays a part in the metabolic pathway, resulting in the inactivation of testosterone and 5alpha-dihydrotestosterone locally in the prostate. The enzyme expressed in the prostate could, therefore, protect cells from excessive androgen action.

Effect of cryoprotective media and freezing techniques on human semen preservation.

With the growing programme of IVF--Et at Lagos University Teaching Hospital the need arise to establish a sperm bank to meet the ever increasing demand at the Hospital for artificial inseminations and in-vitro fertilisation. Fifteen semen samples with count range 50--200 million/ml and motility 30--82% were used. The effectiveness of five synthetic cryoprotectants I, II, III, IV and V and three freezing techniques A, B, and C in cryoperserving human semen were studied. The results were assessed by comparing prefreeze and post thaw sperm motility. Our results using ANOVA (analysis of variance) demonstrated that (1) 7.5% glycerol produced better results than all the other cryoprotectants. (2) Initial freezing in ultralow electrical freezer (-90 degrees c) before storage in liquid nitrogen (-196 degrees c) produced a significantly better post-thaw motility and this was maintained for 4 weeks (table 2). It was therefore concluded that sperm banking can be accomplished in a relatively simple and reliable way using 7.5% glycerol alone and initial freezing in ultralow electrical freezer before storage in liquid nitrogen.