No abstract

The synthesis of dihydrotestosterone is catalyzed by steroid 5a-reductase isozymes, designated types 1 and 2. Mutation of type 2 results in male pseudohermaphroditism, in which the external genitalia are phenotypically female at birth. Two striking and unexplained features of this disorder are that external genitalia of affected males undergo virilization during puberty and that these individuals have less temporal hair regression. The tissue-specific and developmental expression patterns of the 5a-reductase isozymes were investigated by immunoblotting. The type 1 isozyme is not detectable in the fetus, is transiently expressed in newborn skin and scalp, and permanently expressed in skin from the time of puberty. There was no qualitative difference in 5a-reductase type 1 expression between adult balding vs. nonbalding scalp. The type 2 isozyme is transiently expressed in skin and scalp of newborns. Type 2 is the predominant isozyme detectable in fetal genital skin, male accessory sex glands, and in the prostate, including benign prostatic hyperplasia and prostate adenocarcinoma tissues. Both isozymes are expressed in the liver, but only after birth. These results are consistent with 5a-reductase type 1 being responsible for virilization in type 2-deficient subjects during puberty, and suggest that the type 2 isozyme may be an initiating factor in development of male pattern baldness. (J. Clin. Invest. 1993. 92:903-910.) Key words: dihydrotestosterone* sexual differentiation * benign prostatic hyperplasia* prostate cancer * male pattern baldness

The cDNAs for two separate human 17,B-hydroxysteroid dehydrogenases (17p-HSD) have been isolated and sequenced. The well-studied human placental cytosolic 17wB-HSD (also referred to as estradiol dehydrogenase) preferentially catalyzes the reduction of estrone to estradiol-17/3 and the reduction of the C-20-ketone of progesterone to 20-dihydroprogesterone. This isoform of the enzyme has been referred to as 17j8-HSD type 1 and localized to chromosome 17. A second 17fi-HSD isoform (referred to as type 2) is localized in the endoplasmic reticulum of human trophoblast and is characterized by the preferential oxidation of the C-17fi-hydroxyl group of C18-and C19-steroids and the C-20a-hydroxyl group of 20a-dihydroprogesterone. In this study, we determined the chromosomal localization of human 1713-HSD type 2, the expression of this gene in human endometrium, and the tissue distribution of the mRNA. We found that the human 17,B-HSD type 2 gene is localized on chromosome 16, 16q24. 17/8-HSD type 2 mRNA ( 1.5 kb) was identified in human endometrial tissues by Northern analysis of total RNA (10 ,ug). The highest levels of 17.3-HSD type 2 mRNA were found in endometrial tissues obtained during the mid-to late secretory phase of the ovarian cycle (i.e., during the time of high plasma levels of progesterone). 17fi-HSD type 2 mRNA levels were much greater in glandular epithelium than in the stromal cells isolated from secretory phase endometrium. The levels of 17fi-HSD type 2 mRNA in secretory phase endometrium were approximately one-tenth that in villous trophoblast tissue from human placenta. We did not detect 17fi-HSD type 1 mRNA in endometrial tissue by Northern analysis of total (10 ,.g) RNA. These findings are consistent with the view that the progestinregulated 17(3-HSD of the glandular epithelium of the human endometrium is primarily, if not exclusively, the product of the 17fi-HSD type 2 gene. 17f8-HSD type 2 mRNA

This study was conducted as part of an investigation to evaluate the hypothesis that bacterial toxins (LPS or lipoteichoic acid), acting on macrophage-like uterine decidua to cause increased formation of cytokines, may be involved in the pathogenesis of infection-associated preterm labor. We found that cachectin/tumor necrosis factor-a (TNF-a) was synthesized and secreted into the culture medium by human decidual cells and explants in response to treatment with LPS. LPS treatment also caused an increase in PGF2a production by decidual cells and explants. In amnion cells in monolayer culture, TNF-a stimulated PGE2 formation, and TNF-a was cytostatic (inhibited [Hjthymidine incorporation into DNA) but not cytolytic in amnion cells. TNF-a was not detectable (< 0.34 ng/ml) in the amniotic fluid of normal pregnancies at midtrimester or at term before or after the onset of labor (n = 44); but TNF-a was present at concentrations between 2.8 and 22.3 ng/ml in amniotic fluids of 4 of 20 pregnancies with intact membranes complicated by preterm labor (< 34 wk gestational age). LPS was present in 10 of the 20 amniotic fluids of preterm labor pregnancies, including all four in which TNF-a was present. Bacteria were identified in only one of the four LPS-positive, TNF-a-positive fluids. Cytokine formation in macrophage-like decidua may serve a fundamental role in the pathogenesis of preterm labor, including increased prostaglandin formation and premature rupture of the membranes.

Smooth muscle contraction is initiated primarily by an increase in intracellular Ca2", Ca2+-dependent activation of myosin light chain kinase, and phosphorylation of myosin light chain. In this investigation, we identified pregnancy-associated alterations in myosin light chain phosphorylation, force of contraction, and content of contractile proteins in human myometrium. Steady-state levels of myosin light chain phosphorylation and contractile stress were correlated positively in both tissues, but the myometrial strips from pregnant women developed more stress at any given level of myosin light chain phosphorylation. During spontaneous contractions and during conditions that favor maximal generation of stress, the rate and extent of myosin light chain phosphorylation were attenuated in myometrial strips from pregnant women. The content of myosin and actin per milligram of protein and per tissue cross-sectional area was similar between myometrium of nonpregnant and pregnant women. Although cell size was significantly increased in tissues obtained from pregnant women, the amounts of contractile proteins per cellular cross-sectional area were similar. In addition, myosin light chain kinase and phosphatase activities were similar in the two tissues. The content of caldesmon was significantly increased in myometrium of pregnant women, whereas that of calponin (a smooth muscle-specific protein associated with the thin filaments) was not different. We conclude that adaptations of human myometrium during pregnancy include (a) cellular mechanisms that preclude the development of high levels of myosin light chain phosphorylation during contraction and (b) an increase in the stress generating capacity for any given level of myosin light chain phosphorylation. (J. Clin. Invest. 1993. 92:29-37.)