Superoxide dismutase in the prostate lobes of aging Brown Norway rats

BACKGROUND: Spontaneous age-dependent epithelial cell hyperplasia occurs in the lateral and dorsal, but not the ventral, lobes of aging Brown Norway (BN) rats. Diminished antioxidant enzyme activities and increased formation of reactive oxygen species (ROS) promote the pathology of many aging disorders. We investigated the hypothesis that prostatic epithelial cell hyperplasia in the BN rat was related to age-dependent and/or lobe-specific changes in superoxide dismutase (SOD). MATERIALS AND METHODS: Using Western blots, immunohistochemistry and enzyme activity assays we determined the levels of protein expression, subcellular localization, and activities, respectively, of the three SOD isoforms, cytoplasmic SOD1, mitochondrial SOD2, and extracellular SOD3 in the ventral, lateral, and dorsal prostate lobes of 4-month-old rats with normal prostate morphology, in 24-month-old rats with lobe-specific hyperplasia and in older 30-month-old rats. RESULTS: We observed little change in SOD activities as a function of age, although expression of SOD3 increased in the prostatic lobes of older rats. SOD2 levels were higher in the lateral lobe of 4- and 24-month-old rats, but declined by 30 months of age to levels in the ventral and dorsal lobes. SOD1 was localized by immunohistochemistry to the nuclei of epithelial cells in all lobes, but the number of immunopositive nuclei increased in the lateral and dorsal lobes of 24-month-old animals. The concentration of zinc was highest in the prostate lobes of 24-month-old animals. CONCLUSION: Based upon our data, superoxide dismutase is not significantly altered in the rat prostate during aging and thus is unlikely to be an important factor in the evolution of epithelial cell hyperplasia.     

Biochemical and immunohistochemical characterization of prolactin binding in rat ventral,lateral, and dorsal prostate lobes

A radioligand assay and the soluble peroxidase-antiperoxidase (PAP) technique were used to compare ovine and rat prolactin as ligands for the demonstration of prolactin binding sites in rat ventral, lateral, and dorsal prostate lobes. Biochemical techniques were effective in demonstrating prolactin binding sites in ventral prostate with both ovine and rat prolactin; however, binding sites could not be characterized in lateral or dorsal lobes with either ligand. Using the PAP technique, rat prolactin consistently produced a discrete, dense reaction product over binding sites in the Golgi zone of the ventral prostate; ovine prolactin produced a more dispersed pattern of staining throughout the entire supranuclear region of the cells. In ventral prostate, most epithelial cells were immunoreactive when either ligand was used. However, lateral prostate contained fewer densely immunoreactive cells than did ventral prostate, and rat prolactin was more effective in demonstrating these binding sites than was ovine prolactin. Dorsal prostate epithelium was highly immunoreactive for binding of both ligands; however, there was considerably more staining in this lobe that remained after absorption of the antibody with prolactin. These data suggest that the inability to demonstrate prolactin binding sites in the lateral lobe using radioligand assay may have been due to the fewer numbers of binding sites that were diluted below the sensitivity of the assay when a tissue homogenate preparation was used. Noncompetitive binding in the dorsal lobe, as seen in the radioligand assay, coincided with immunocytochemical findings of relatively high nonabsorbable background staining.     

Reverse zymography studies of protease inhibitors in the secretions of different lobes of rat prostate

The purpose of this study was to determine whether protease inhibitors were a constituent of secretions from the different lobes of the rat prostate. A reverse zymography method was used employing gelatin substrate-SDS-polyacrylamide gel electrophoresis to detect inhibitors of trypsin in secretions of the ventral, lateral, and dorsal prostate lobes of the Sprague-Dawley rat. Inhibitors of approximately 34 and 63 kDa were detected in ventral prostate secretion and of about 63 and 73 kDa were found in lateral lobe secretion. However, no inhibitor activities were detected in secretions of the dorsal lobe. The protease inhibitors of ventral prostate secretion were partially purified by preparatory isolectric focusing and SDS-polyacrylamide gel electrophoresis. The 34-kDa (pI 5.6-6.4) inhibitor had a higher activity against trypsin, whereas the 63-kDa (pI 6.4-7.0) inhibitor was more active against chymotrypsin. The rat prostate appears to have a lobe-specific distribution of secretory serine protease inhibitors.     

A local direct effect of pituitary graft on growth of the lateral prostate in rats.

Prolactin and testosterone are synergistic in stimulating growth of the rat prostate. The lateral lobe is more sensitive to this synergism than the ventral and dorsal lobes. To investigate whether prolactin acts directly in the rat prostate or indirectly through another systemic mediator, anterior pituitary grafts (1 mm3) were implanted in the lateral prostate of castrated Sprague-Dawley rats in whom a 0.5 cm or 1.0 cm testosterone-filled silastic tubing was implanted subcutaneously at the same time. Rats were randomly assigned to receive either the pituitary or a muscle chip of similar size grafted beneath the fascia lateral to the lateral prostate. Twenty-one days later, serum prolactin levels were not elevated in pituitary-grafted animals and were not significantly different from those in muscle-grafted rats. The mean lateral prostate weight on the grafted side in pituitary-implanted rats with 1.0 cm testosterone tubing was 43% heavier than either that of the contralateral side or the corresponding weights in muscle-implanted rats. In pituitary-implanted rats with 0.5 cm testosterone tubing, the mean lateral prostate weight on the grafted side was 60% heavier than either that of the contralateral side or that of the corresponding weights in muscle-implanted rats. The weight of the ventral and dorsal lobes of the prostate was not significantly affected by the presence of pituitary grafts in one of the lateral lobes. The local effect of prolactin on the lateral prostate was further demonstrated by an overall decline in tissue concentrations of dihydrotestosterone in the grafted side. These results provided evidence to indicate that there was a direct effect of prolactin on growth of the lateral prostate in rats.     

Immunocytochemical localization of metallothionein in the rat prostate gland

Metallothionein (MT), which binds zinc and other metals, was localized within the rat prostatic complex at light and electron microscopic levels utilizing immunocytochemistry. Two groups of mature, male Sprague-Dawley rats were injected with cadmium chloride subcutaneously (2 mg/kg body weight) to induce the synthesis of MT, and were sacrificed 48 h postinjection. From the first group, prostatic tissue from the three lobes was prepared for light microscopy. The indirect peroxidase antiperoxidase procedure was used for MT localization using rabbit anti-MT as the primary antibody. The three lobes of the rat prostate demonstrated a positive reaction for MT, but among the lobes variations in the intensity and localization of the reaction product occurred. Tissues from the second group of animals were prepared for electron microscopy. Using the indirect immunogold labeling technique with anti-MT, MT localization was confirmed in the rough endoplasmic reticulum, secretory vesicles, secretory products, and subepithelial connective tissue. These localizations suggest that MT binds zinc both intra- and extracellularly, where it may function in zinc storage and metabolism.     

An anatomic and histologic study of the rat prostate

Various morphologic features of the rat prostate complex were characterized by anatomic dissection and by light microscope histology. The prostate complex is viewed as a whole and it is related to the individual portions of the male reproductive system. The three lobes of the prostate are designated as ventral, lateral, and dorsal according to their relation to the urethra. These lobes are connected to the urethra by fascia and a series of ducts. Relations of the prostate to the seminal vesicles, coagulating glands, vas deferens and ampullary glands, urinary bladder, and ureters are described. Vascular supply is also reviewed. While the acinar pattern of each prostatic lobe is unique, the dorsal and lateral lobes more closely resemble each other than the ventral lobes.     

Comparative contractile responses among ventral, dorsal, and lateral lobes of the rat prostate

Prostatic zonal heterogeneity as a factor influencing urogenital smooth muscle contractile mechanisms was evaluated in the dorsal, lateral, and ventral lobes of the sexually mature rat. Additionally, using the ventral lobe, we assessed the role of the prostatic capsule to determine its contribution to tissue contractility. Smooth muscle contractile responses were determined for the alpha-adrenergic agonists norepinephrine and methoxamine; the cholinergic agonist carbamylcholine; the alpha 2-adrenergic agonist UK-14,304; serotonin; and potassium chloride. The dorsal, lateral, and ventral lobes contracted in response to all agonists. In the three lobes, norepinephrine was the most potent contractile agent; alpha 2 receptor activation with UK-14,304 resulted in the lowest maximum response. Carbamylcholine and serotonin were only weak contractile agonists in all three lobes. Maximum contractile responses to alpha agonists were greatest in the ventral prostate relative to the other two lobes, based on contractile responses to norepinephrine and methoxamine relative to KCl. The contractions of the ventral lobe in the presence and absence of the capsule were similar; thus the observed responses were not enhanced by the capsule but were attributable primarily to the presence of prostatic smooth muscle. Insofar as these studies with anatomically distinct lobes in the rat may reflect zonal homology in other species, these results support the contention that all zones may contribute to prostatic contractility.     

Regional variations in the testicular dependence of prolactin binding and its possible relationship to castration-induced involution in rat prostate gland

Prolactin binding sites of ventral, lateral, and dorsal lobes of rat prostate were examined immunohistochemically 1, 2, 4, and 8 days after castration or sham operation. In sham-operated rats each lobe exhibited a distinct pattern of intracellular and intraluminal prolactin binding. A loss in prolactin binding from epithelial cells of ventral prostate, which was visualized postcastration, was quantitated with the aid of an image analyzer and then statistically evaluated. The proportion of ventral prostate epithelial cells devoid of prolactin binding increased from approximately 13% in sham-operated rats to approximately 29% 1 day after castration, and reached a peak level of about 71% 4 days postcastration. No loss of prolactin binding was evident in either lateral or dorsal prostate up to 8 days postcastration. Direct measurement of epithelial cell heights and subsequent statistical evaluation revealed similar regional differences in the rates and extent of prostate involution. Eight days after castration ventral prostate epithelial cell heights decreased by 56% whereas lateral and dorsal lobe epithelial cells heights decreased about 25% and 14%, respectively. The apparent relationship between testicular dependence of prostatic prolactin binding and castration-induced prostatic involution are discussed in terms of possible regional variations in the prolactin-androgen interplay in prostate.     

The effect of orally administered cadmium on the ultrastructure of the rat prostate

Summary The effects of cadmium and nickel chloride, administered in drinking water at 5 and 50 ppm, on the rat prostate are described. Zinc concentrations in the two lobes of the gland were unaffected by the metals and no consistent changes were observed at the subcellular level by X-ray microanalysis. The ultrastructural appearance of the prostate gland in rats of varying ages was unaltered following cadmium administration at those levels, while plasma testosterone concentrations did not differ significantly in cadmium treated animals. Low levels of cadmium (5 ppm) were accumulated by the ventral lobe of the prostate, although the metal was not detectable subcellularly. The results are discussed in relation to human prostatic carcinoma.     

The development of vascular supply of normal rat prostate during the sexual maturation: an angiographic study.

Vascular distribution of small blood vessels and capillaries using India ink angiography was studied in normal rat prostate from puberty up to full sexual maturation. The study included both macroscopic observation of the lobular vascular irrigation and the histological assessment of the periacinar capillary network. The topographical distribution of the main prostate branches was found to be different among the rat prostate lobes. The ventral lobe seems to be better irrigated than the dorsal one. The former being supplied by two parallel vascular systems, one irrigating the median two-thirds of the ventral lobe, whereas the remaining external one-third was found to be conjointly irrigated from the pericapsular branches of the fat pads. The blood vessels of the dorsal and lateral lobes emerged radially from a periurethral circle, with the dorsal branches ending blindly in the connective tissue of the pelvic cavity, whereas the lateral prostate was also conjointly irrigated by a dual vascularization from the pericapsular fat pad and the periurethral circle branch. The histological study revealed quantitative differences between the periacinar capillaries of both ventral and dorsal lobes. The capillary density was found to be age dependent and directly proportional to the acinar size. Small acini were less well irrigated by capillaries than were the larger ones. The number of capillaries per acinar area increased progressively toward the maturation (day 90); thereafter, their number remained constant. Both prostate lobes showed identical patterns. The heterogeneous vascular networks among the rat prostatic lobes might offer an additional clue for their distinctive morphophysiological characteristics, which most probably play a role in various pathogenetic processes.     

Reduction in prostatic concentration of endogenous dihydrotestosterone in rats by hyperprolactinemia

Persistently high levels of circulating prolactin can be achieved in male rats when pituitaries from female donors are grafted under the renal capsule. Enhanced growth of the lateral prostate can be accomplished by an apparent synergistic effect of excess prolactin with subphysiologic doses of testosterone. To define this effect we measured the endogenous dihydrotestosterone (DHT) concentrations in rat prostate lobes. Twenty Sprague-Dawley male rats (250 g) were castrated and given subcutaneous implants of silastic tubing filled with 1 cm of crystalline testosterone. Ten of these rats simultaneously received two pituitary grafts under the renal capsule. The remaining ten rats received intrarenal skeletal muscle grafts as controls. Four weeks later, the weight (mg +/- SE) of the ventral and dorsal lobes were not significantly different between the two groups, while the lateral lobe was significantly (P less than 0.01) heavier in rats with pituitary grafts (121.4 +/- 7.5) than in controls (81.7 +/- 10.4). Endogenous DHT in the tissue extracts was determined by radioimmunoassay following KMnO4 treatment to eliminate testosterone. The concentration of DHT (ng/g tissue +/- SE) was significantly (P less than 0.01) lower in the lateral prostate of graft-bearing animals (4.40 +/- 0.29) than in the controls (5.98 +/- 0.34). These results indicate that, in the rat, hyperprolactinemia induced by pituitary grafts is associated with a heavier lateral prostate and a lower concentration of endogenous DHT in that tissue. These results also suggest that the action of prolactin in the rat prostate is not mediated through the action of androgen.     

Proteins of the rat prostate: I. Preliminary characterization by two-dimensional electrophoresis

The rat prostate consists of three distinct lobes: the ventral, lateral, and dorsal. Proteins in the three lobes of the prostate were studied with the ISO-DALT system for high-resolution two-dimensional electrophoresis. Proteins were detected with ammoniacal silver stain. Comparison of patterns from the three lobes of the prostate of control, noncastrated rats revealed that while there was a remarkable overall similarity, six groups of proteins showed lobe-specific differences. When prostatic regression was induced by castration, androgen-dependent proteins showed a decrease in staining intensity. A group of proteins, with pI 5.0-6.0 and MW 65,000-70,000, was consistently observed only during the active phase of prostatic regression (days 3-7 postcastration). Their presence during this specific interval may play a role in tissue involution.     

Engineered FGF-2 expression induces glandular epithelial hyperplasia in the murine prostatic dorsal lobe

OBJECTIVE: It is known that androgens and stromal-epithelial interactions are required for the formation and growth of the prostate. FGF-2 is overexpressed in prostatic stromal cells in benign prostatic hypertrophy (BPH)/prostate cancer. This supports the paracrine/autocrine growth of prostatic epithelial/stromal cells in the pathogenesis of BPH and invasive prostate cancer. METHODS: We established transgenic mice expressing FGF-2 under the control of a short rat probasin promotor. FGF-2 transgenic founder mice expressing FGF-2 in the prostate were infertile. Thus, male founder mice were sacrificed for histological analysis. RESULTS: FGF-2 was expressed in epithelial cells in glands of the dorsal, lateral, and ventral prostatic lobes of two FGF-2 transgenic founder mice, but not in the anterior lobe of transgenic mice or in any lobe of non-transgenic control littermates. Acinar epithelial glands in dorsal prostatic lobes of FGF-2 transgenic mice expressing FGF-2 were more dense and showed simple papillary hyperplasia of epithelial cells compared with those of control littermate mice. Glandular and luminal enlargement without epithelial growth was observed in the ventral lobe of FGF-2 transgenic mice compared with the controls. CONCLUSION: In conclusion, FGF-2 transgenic mice under the control of rat probasin promoter showed simple epithelial hyperplasia in glands of the prostatic dorsal lobe and glandular enlargement without epithelial growth in the prostatic ventral lobe.     

Effect of hyperosmotic substances injected into the prostate of Wistar rats

PURPOSE: To verify the effects produced by the injections of hyperosmotic substances into the prostate of Wistar rats as judged by gland weight, behavior, histologic changes, and systemic electrolytic alterations. MATERIALS AND METHODS: A total of 42 Wistar rats were divided into five groups and treated in the following manner. In Group I (N = 6), the abdominal cavity was opened and closed. In Group II (N = 6), a needle was introduced into the each ventral lobes of the prostate gland. In Group III (N = 10), a 0.9% sodium chloride solution was injected into the each ventral lobe of the prostate gland. In Group IV (N = 10), a 20% NaCl solution was injected into the each ventral lobe of the prostate gland. In Group V (N = 10), a 50% glucose solution was injected into the each ventral lobe of the prostate gland. The following parameters were studied: histologic features of the ventral lobes of the prostate, the electronic weight of the parts utilized in the surgery, and the sodium and potassium concentrations. RESULTS: The animals of Group V (50% glucose solution) were sacrificed after 60 days and showed a significant reduction in the weight of the ventral prostate lobes in comparison with the other groups (P = 0.05). There were important histologic changes in the groups which received hyperosmotic substances. After the 50% glucose injection, the potassium level increased temporarily. CONCLUSIONS: The injection of 50% glucose solution produced significant alterations in the tissue structure, with reduction in prostatic weight. The electrolyte changes were transitory.     

Immunohistochemical localization of metallothionein in the rat prostate gland during postnatal development

Immunocytochemical and electrophoretic techniques were used to investigate the presence of metallothionein, a metal-binding protein, in the dorsolateral and ventral lobes of the developing rat prostate. Male rats aged 7 and 14 days were injected subcutaneously with 6 and 20 mg/kg body weight of cadmium and zinc, respectively, or with saline for controls, 24 h prior to tissue sampling. Immunohistochemical localization of metallothionein was observed in the epithelial tissues of the dorsolateral prostate from 7 and 14 day-old animals and in 1 day-old untreated rats. This staining pattern did not appear to be significantly affected by cadmium or zinc treatment. In contrast, metallothionein localization in the ventral prostate decreased with age but demonstrated a slight response to metal-ion treatment in the 7 day-old animals. Electrophoretic and immunoblot analysis confirmed the presence of metallothionein in the control and metal-induced prostate samples from neonatal rats. Lobe-specific differences in localization suggest a functional significance for metallothionein, independent of inducible protein.     

Effects of androgens on the ultrastructure and subcellular zinc distribution in the prostatic epithelium of castrated rats

Sprague Dawley rats were maintained on testosterone propionate or 5 alpha-dihydrotestosterone for 3 days following bilateral orchidectomy for a 7-day period. Ultrastructural examination showed only partial recovery of the prostatic epithelium with testosterone propionate while 5 alpha-dihydrotestosterone caused the lateral and ventral lobes to revert to the appearance of control tissues. The latter metabolite induced greater stimulation of the prostate evidenced by increased mitotic division of the epithelial cells and an increased number of basal cells exhibiting ciliary formation was observed. Zinc concentrations in subcellular regions of both lateral and ventral prostate lobes were affected by the two androgens. Testosterone propionate was most effective in elevating zinc in the lateral lobe, particularly within the secretory components. In the ventral lobe both androgens caused an increase in subcellular zinc concentrations above control levels. The increase of nuclear and nucleolar zinc was related to the increase in nuclear activity and cellular response to the androgen administration.     

A systematic study of biochemical differences between the lobes of the rat prostate

The present study constitutes a systematic search for biochemical parameters which could be used to monitor the isolated function of various prostate lobes and accessory sex glands in the rat. Various parameters were measured in the 105 000 × g supernatants of the ventral, lateral and dorsal prostate lobes, and in the coagulating glands and seminal vesicles. These included spermine, citric acid, acid phosphatase, fructose and zinc, as well as the pattern of proteins in both cytosols and secretions, which were determined using one dimensional SDS, polyacrylamide gel electrophoresis. The results suggest that several parameters can be used including: Ventral lobe – spermine or prostatein; Lateral lobe – zinc or a 15 000 dalton protein; Dorsal lobe – spermine or a 60 000 dalton protein; and coagulating gland – fructose.     

Two-dimensional electrophoresis of proteins from different lobes of the rat prostate and seminal vesicle

Two-dimensional ISO-DALT electrophoresis of cytosols and secretions from various lobes of the rat prostate gland and seminal vesicle reveals major differences in intracellular and secretory protein patterns. This study confirms a previous study utilizing one-dimensional electrophoresis. The dorsal lobe and coagulating gland appear to secrete predominantly relatively basic proteins (molecular mass, MM, 70,000–200,000 daltons, pI > 7) in contrast to the ventral lobe, which secretes proteins of a more acidic character (pI 4–5). The majority of proteins in the latter case appear to represent subunits of the major secretory protein of the rat ventral prostate, prostatein. At least one secretory protein is relatively specific for the lateral lobe (MM 16,000 daltons, pI 4.5). The vesicular secretion also contains relatively greater quantities of basic proteins than acidic but with varying molecular mass (12,000–100,000 daltons). This study extends the search for specific protein markers for different lobes of the rat accessory sex glands and provides additional biochemical data which can be exploited in the future to isolate selected secretory proteins on a large scale for antibody production.