Defects in cortisol-metabolizing enzymes in primary open-angle glaucoma.

Assays of cortisol-metabolizing enzymes in homogenates of human trabecular meshwork cells under optimal conditions revealed two defects in primary open-angle glaucoma (POAG): one is a marked increase in delta 4-reductase and the other is a decrease in 3-oxidoreductase. Experiments indicated that the differences in enzyme activities seen between POAG and nonPOAG trabecular meshwork derived cell homogenates were due to altered amounts of enzymes rather than to alterations in cofactor availability, pH, or endogenous activators or inhibitors. This clearly demonstrates an enzymatic defect(s) in POAG which may be the basis for the ocular hypertension and sensitivity to exogenous glucocorticoids seen in this disorder.

Altered cortisol metabolism in cells cultured from trabecular meshwork specimens obtained from patients with primary open-angle glaucoma.

Cells cultured from trabecular meshwork specimens obtained from patients with primary open angle glaucoma (TMPOAG cells) exhibited two major differences in cortisol-metabolizing enzymes when compared with similar cells from nonglaucomatous patients. One is a marked increase (greater than 100-fold) in delta 4-reductase activity and the other is a decrease (4-fold) in 3-oxidoreductase activity. Peripheral lymphocytes from one of these patients as well as from five additional patients with POAG, did not show these abnormalities, indicating that the defects are not found in all cortisol-metabolizing cells. The abnormal metabolism of cortisol by TMPOAG cells may be of significance in the pathogenesis of POAG.

Phenytoin effect on the proliferation of rat oral epithelium is mediated by a hormonal mechanism.

Systemic pretreatment of male rats with phenytoin (PHT) (30 mg/100 g body weight) significantly (P less than 0.001) increased mitotic frequency, shortened mitotic duration and renewal time in the basal cells of the oral epithelium. This effect of PHT was abolished by simultaneous s.c. injection of cyproterone acetate (CyA) (50 micrograms/100 g body weight) or by castration. CyA treatment of intact rats or castration further decreased mitotic frequency, prolonged mitotic duration and turnover time in the oral epithelium. The effect of castration was reversed by the simultaneous s.c. injection of testosterone propionate (Tp) (50 micrograms/100 g body weight). These results suggest that PHT effect on epithelial proliferation is mediated by a hormonal mechanism.

The effect of 5,5'-diphenylhydantoin on the metabolism of 17 beta-estradiol by rat oral mucosa.

Systemic pretreatment of rats with 5,5'-diphenylhydantoin (DPH) or its addition into an in vitro assay increases microsomal hydroxylation of 17 beta-estradiol. This increase depends on the concentration of DPH in the microsomal cell compartment.

Effect of ethanol intake on cellular regulation of testosterone-5 alpha-reductase in rat oral tissues.

The effect of ethanol on testosterone-5 alpha-A-ring reductase activity was studied in the whole homogenate and/or subcellular fractions (microsomes and cytosol) of buccal mucosa, gingiva, liver and prostate from intact ethanol-fed (36% of dietary calories were given as ethanol for up to 360 days) and pair-fed control rats. An increased enzyme activity was found in the hepatic, prostatic and gingival homogenates from ethanol-fed rats. No difference in the enzyme activity was seen in the homogenates of buccal mucosa. However, when the buccal mucosal microsomal fraction was used a significant (P less than .005) increase in the enzyme activity was found in the ethanol-fed rats. It was determined that the lack of an increase in 5 alpha-reductase activity in the buccal mucosal homogenates from ethanol-fed rats was due to the presence of a cytosolic inhibitor of this enzyme. Enzyme kinetics showed a decrease in the velocity in correlation with the increasing concentration of cytosolic inhibitor (Vmax control = 1.9 and Vmax ethanol = 1.7, 1.45 and 1.0 nmol, respectively). The apparent Km (0) and Kp (1--3) values were similar for all combinations (4.5 x 10(-5) M). In addition, a similar Ki constant (2.2 mg of cytosolic protein) was found for different testosterone concentrations. These results suggest that the ethanol-induced cytosolic inhibitor in buccal mucosa combines with the enzyme, independent of the substrate and inhibits it by an allosteric mechanism. Studies using dialysis, heating and tryptic digestion suggests that the inhibitor is a protein.

Effect of chronic alcohol ingestion on the biosynthesis of steroids in rat testicular homogenate in vitro.

The activity and kinetics of delta 5-3 beta-dehydrogenase and 17 alpha-hydroxylase, using labeled pregnenolone as substrate, were measured in gonadal homogenates from rats fed alcohol or isocalorically substituted carbohydrate for 40 days. There was no difference in the rate or reaction kinetics for either enzyme noted between control and alcohol-treated animals when the assays were carried out in the presence of saturating amounts of exogenous pyridine nucleotide cofactors. However, when exogenous cofactors were omitted from the reaction mixture, there was decreased activity of the delta 5-3 beta-dehydrogenase system and increased activity of the 17 alpha-hydroxylase reaction. Furthermore, a cofactor-specific inhibiting effect on delta 5-3 beta-dehydrogenase activity by NADH and NADPH was found. Incubation of gonadal homogenates from the alcohol-treated animals with pyruvate on lactate (in the absence of exogenous cofactors) resulted in an increase and a decrease, respectively, in enzyme activity. These studies indicate that chronic alcohol use decreases gonadal delta 5-3 beta-dehydrogenase activity and that this is most likely due to an effect of the agent on the concentration and/or availability of pyridine nucleotide cofactors rather than to a direct effect on the enzyme. This phenomenon may account for the mechanism by which alcohol decreases testosterone secretion in these animals.

Concentration of circulating hormones and metabolism of androgens by human gingiva.

The present study evaluates the relationship between periodontal status, concentration of circulating hormones and metabolism of androgens by human male and female gingiva in vitro. In both male and female patients with healthy gingiva the plasma concentration of gonadotropins (LH and FSH) and steroid hormones (testosterone, androstenedione, estradiol-17 beta, progesterone and cortisol) were in a normal range. However, an alteration in the plasma concentration of progesterone was found in both male and female patients with periodontal pathosis. Both androgens (testosterone and androstenedione) were readily metabolized by human gingiva tissue in vitro. The major pathway of the metabolism of testosterone was via the formation of 17 beta-hydroxy-5 alpha-A-ring reduced androgens (5 alpha-dihydrotestosterone and 3 alpha-, 3 beta-androstanediol). In contrast, androstenedione was metabolized mainly to 17-keto-5 alpha-A-ring reduced (5 alpha-androstanedione, androsterone and epiandrosterone) and 17 beta-oxidoreduced (testosterone) compounds. In addition both substrates were metabolized to 5 beta-A-ring reduced androgens (5 beta-dihydrotestosterone, 5 beta-androstanediol and 5 beta-androstanedione). A significant feature of the metabolism of testosterone and androstenedione by inflamed gingiva was an increase of 5 alpha-A-ring reductase activity (mainly the formation of 5 alpha-dihydrotestosterone and 5 alpha-androstanedione) and 17 beta-oxidoreductase activity (mainly the formation of testosterone from androstenedione). The increase in 5 alpha-reductase activity also showed a significant correlation with the plasma progesterone concentration.