Sex hormones and metabolism of glycosaminoglycans. I. Effect of orchidectomy and administration of testosterone in rabbits

Glucosamine-6-phosphate synthase--the multi-facets enzyme

L-Glutamine: D-fructose-6-phosphate amidotransferase, known under trivial name of glucosamine-6-phosphate synthase, as the only member of the amidotransferase subfamily of enzymes, does not display any ammonia-dependent activity. This enzyme, catalysing the first committed step in a pathway leading to the eventual formation of uridine 5'-diphospho-N-acetyl-D-glucosamine (UDP-GlcNAc), is an important point of metabolic control in biosynthesis of amino sugar-containing macromolecules. The molecular mechanism of reaction catalysed by GlcN-6-P synthase is complex and involves both amino transfer and sugar isomerisation. Substantial alterations to the enzyme structure and properties have been detected in different neoplastic tissues. GlcN-6-P synthase is inflicted in phenomenon of hexosamine-induced insulin resistance in diabetes. Finally, this enzyme has been proposed as a promising target in antifungal chemotherapy. Most of these issues, especially their molecular aspects, have been extensively studied in recent years. This article provides a comprehensive overview of the present knowledge on this multi-facets enzyme.

Glycosaminoglycans in the three lobes of the rat prostate following castration and testosterone treatment

Androgen dependence of glycosaminoglycans (GAGs) in the prostate was studied using tissue from intact (sham control), castrated, and androgen-treated castrated rats. GAGs from the ventral, dorsal, and lateral lobes of the prostate were isolated and characterized by cellulose electrophoresis using appropriate GAG standards and enzymatic digestion or nitrous acid hydrolysis. Androgen deprivation was initiated by castration and rats were sacrificed at various time intervals after 7 days castration. After castration, the total GAG content decreased in three prostate lobes. At day 7 after castration, the total hyaluronic acid (HA) content decreased by 74% (ventral lobe) and 34% (lateral lobe) compared with the sham control. No effect was observed for HA content in the dorsal lobe. Castration decreased the total heparan sulphate (HS), dermatan sulphate (DS), and chondroitin sulphate (CS) contents in the three prostate lobes at 0 days of treatment, except for the CS content in the dorsal and lateral lobes. Androgen replacement increased the total GAG contents in the three prostate lobes. At 14 days of testosterone propionate treatment, there were 9-, 6.8-, 4.1- and 3.7-fold increases in HA, HS, DS, and CS, respectively, in the ventral lobe. These increases were more rapid and profound in the ventral than in the dorsal and lateral lobes. These findings indicate that all GAGs are regulated by androgen and there may be lobe-specific differences in their regulation. This could be a function of the heterogeneous populations of cells in each lobe.

Influence of testosterone on chondroitin sulphate proteoglycan in the rat prostate

There are recognized interactions between prostatic stromal and epithelial cells. These interactions may be influenced by the composition of the extracellular matrix, which is composed of proteins such as collagen, laminin, fibronectin, and proteoglycans (PGs) such as chondroitin sulphate proteoglycan (CSPG). In our continuing studies on prostate biology, we examined the three lobes of the normal adult rat prostate, i.e., ventral, dorsal, and lateral, for CSPG by indirect immunofluorescence, using an immunospecific monoclonal antibody (CS-56) for the chondroitin sulphate (CS) moiety of the PG. Staining of the prostate sections with CS-56 antibody followed by labelling with IgG fluorescein isothiocyanate conjugate indicated strong fluorescent signals associated with the ventral lobe basement membrane. The signal was stronger and more continuous in the distal acini than in the proximal acini. The staining of the dorsal and lateral lobes was less intense than that of the ventral lobe. Following castration of the rats, the basement membrane staining became discontinuous. Androgen replacement by administration of testosterone propionate (TP) reversed the effects of castration. Quantification of the total CS content showed decreases of about 60% in the ventral and lateral lobes after castration. TP administration for 14 days increased the total CS content several fold above the values for castrated rats in all lobes. The results demonstrated that CS content was significantly higher for TP-treated animals, suggesting that the expression of prostate CSPG is regulated by androgens. This approach should be useful in the study of the extracellular matrix in prostate biology.

Effects of androgens in models of rheumatoid arthritis

Testosterone and its metabolite 5 alpha-dihydrotestosterone (DHT) were compared with dexamethasone 21-acetate in two different animal models of arthritis and found to have effects on cartilage breakdown and inflammation. In the mouse air pouch, at the three dose levels used, significant effects were obtained with DHT and were more pronounced on cartilage breakdown than on inflammation. At the lowest dose of 0.3 mg kg-1 there was a 64% inhibition of collagen breakdown and 18% inhibition of glycosaminoglycans (GAGs) breakdown. In the antigen-induced arthritis mouse model testosterone had significant inhibitory effects on inflammation (synovial hyperplasia) and cartilage erosion.

Ultrastructural localization of proteoglycans by cationic dyes in the epithelial-stromal interface of the guinea pig lateral prostate

Proteoglycans (PGs) in the epithelial-stromal interface of the guinea pig lateral prostate were localized at ultrastructural level, using cuprolinic Blue (CB), alcian Blue (AB), and ruthenium red (RR). After staining with CB or AB according to the critical electrolyte concentration method (CEC), PGs appeared as short electron-dense filaments. According to their sizes and location, three type (T1, T2, T3) of CB-stained filaments were identified. T1 filaments were short (25 nm) and were found on both sides of the lamina densa of the basal laminae of the prostatic epithelium, smooth muscle cells, and capillary endothelial cells. They were regularly spaced with an interval of 60 nm. T1 filaments were more randomly distributed in the lamina densa. T2 CB filaments were approximately 30-40 nm long and closely associated with the collagen fibrils. They were usually arranged perpendicular to the long axis of collagen fibrils also at intervals of 60 nm. T3 filaments were found in different regions of the lamina propria, including: 1) reticular layer (pars fibroreticularis) below the basal lamina; 2) interstitial spaces; 3) closely associated with the cell surfaces of fibroblasts; and 4) around the collagen fibrils. Their sizes were variable (60-100 nm) and more densely stained. AB revealed similar patterns of PG distribution, except that the three types of PG filaments were longer but thinner. When the tissues were stained with RR, or RR-AB combined, PGs appeared as dense granules of various sizes, instead of filaments. Their locations and distributions were similar to those of the CB filaments, except that in the case of combined RR-AB treatment the PG granules were linked by a fine filamentous network, suggesting the interconnecting nature of the PGs and other extracellular components.

Gender and baboon aortic steroid hormone receptors

To examine the potential of steroid hormones to serve as putative regulators of aortic cell function, we defined hormone receptor content and distribution in intact baboons. Total androgen receptor content in baboon aortic arch, thoracic arch, and abdominal aorta of young mature males was indistinguishable from that of proestrus females. However, 30% to 40% of male aortic androgen receptors were in the nuclear fraction, whereas all aortic androgen receptors of proestrus females were in the cytoplasmic fraction. Cytoplasmic fraction estrogen receptor content of aortic arch and thoracic aorta of intact males was indistinguishable from that of proestrus females. However, cytoplasmic fraction estrogen receptor content of abdominal aorta of proestrus females was significantly greater than that of males. Nuclear fraction estrogen receptors were not detectable in either male or proestrus female baboon aortas. To assess effects of endogenous estrogen on aortic progesterone receptor content, we quantified cytoplasmic fraction progesterone receptors and found that content of proestrus female aortic arch was not significantly different from that of males. However, cytoplasmic fraction progesterone receptor content of thoracic and abdominal aorta of proestrus females was significantly higher than that of males. To determine whether differences in aortic receptor content or distribution were associated with changes in aortic cell function, we quantified the activity of two enzymes of glycosaminoglycan metabolism. Aortic beta-glucuronidase activity was not different in male or proestrus female baboons.(ABSTRACT TRUNCATED AT 250 WORDS)

The glycosaminoglycans of normal and hyperplastic prostate

A study has been made of the glycosaminoglycans (GAG) of the fetus, normal adult, and benign hyperplastic prostate. In the adult normal prostate dermatan sulphate (DS) is the predominant GAG. The central zone has a slightly higher chondroitin sulphate (Ch AC) content than the peripheral zone. Fetal prostates (22-27 weeks gestation) contain no heparan sulphate (HS). Benign prostatic hyperplasia (BPH) has an increased content of Ch AC. On separation of BPH stroma and epithelium, the epithelial fraction contains only Ch AC and DS. HS and hyaluronic acid (HA) are confined to the prostatic stroma.