Comparison of spontaneous and experimentally induced canine prostatic hyperplasia

Spontaneous prostatic hyperplasia in the beagle appears to progress with age from a glandular to a cystic histological appearance. Prostatic hyperplasia can be induced in young beagles with intact testes by treatment for 4 mo with either dihydrotestosterone or 5 alpha-androstane-3 alpha, 17 beta-diol, alone, or with either of these steroids in combination with 17 beta-estradiol. In contrast, the induction of prostatic hyperplasia in young castrated beagles, in which the gland had been allowed to involute for 1 mo, requires the administration of both 17 beta-estradiol and either 5 alpha-androstane-3 alpha, 17 beta-diol or dihydrotestosterone. Testosterone and 17 beta-estradiol, either singly or in combination, did not produce the hyperplastic condition in intact or castrated beagles. The experimentally induced prostatic hyperplasia is identical in pathology to the glandular hyperplasia that occurs naturally in the aging dog with intact testes. However, cystic hyperplasia was not produced by any of the treatments tested in young animals.

Dihydrotestosterone in prostatic hypertrophy. II. The formation and content of dihydrotestosterone in the hypertrophic canine prostate and the effect of dihydrotestosterone on prostate growth in the dog

Three types of studies have been performed in immature, mature, and hypertrophic prostate glands of the dog. First, the concentrations of testosterone and dihydrotestosterone have been measured in the three types of gland. Dihydrotestosterone was the predominant hormone recovered in all prostates studied and was present in approximately five times higher concentration in the hypertrophic as compared to the other types of dog prostate. Second, pharmacological doses of dihydrotestosterone were administered to castrated dogs for 9 months and resulted in a distinct acceleration of prostatic growth as compared to testosterone treatment. Third, the rates of formation and degradation of dihydrotestosterone were measured in normal and hypertrophic tissue and were found to be essentially the same. These observations suggest that dihydrotestosterone accumulation may be causally linked to the development of canine prostatic hypertrophy. However, the mechanism by which dihydrotestosterone accumulates in the prostate remains to be determined.

Spontaneous benign prostatic hyperplasia in the beagle. Age-associated changes in serum hormone levels, and the morphology and secretory function of the canine prostate

This paper is a cross-sectional study of spontaneous benign prostatic hyperplasia (BPH) in a single canine species. The effects of aging and hormonal changes on the growth, histology, and glandular secretory function of the canine prostate were studied in 42 male beagles ranging in age from 8 mo to 9 yr. The beagle prostate enlarges for at least 6 yr, whether normal or hyperplastic. In contrast, prostatic secretory function, determined by ejaculate volume and total ejaculate protein, declines markedly after 4 yr of age. These reciprocal growth and functional changes in the prostate are closely associated with a progressive increase in the incidence of BPH, which is already apparent in some dogs by age two. With age there is a modest decrease in serum androgen levels with no apparent change in serum 17 beta-estradiol levels. This suggests that the growth and functional changes that are associated with the development of BPH and are initiated very early in life reflect an altered sensitivity of the prostate to serum androgens or a response to the relative decrease in the serum androgen to estrogen ratio.

Development of canine benign prostatic hyperplasia with age

The prevalence and growth of benign prostatic hyperplasia (BPH) in beagles as a function of age were studied. The normal prostate gland was 12 +/- 3 gm in beagles 2.1-3.0 years of age; this weight remained unchanged unless BPH developed. Histologic evidence of BPH developed at an early age with a prevalence of 16% of the dogs by the age 2 years. Fifty percent of the dogs had BPH, determined histopathologically by age 4.1-5.0 years. The average weight of the prostate gland remained constant until after age 8 years. With age, the pathologic features of BPH changed from glandular to the complex form, with no increase in prostate weight until after 8 years. Reinitiation of growth occurred and prostate weight increased to greater than 36 gm in eight of 185 beagles older than age 8 years.

Androgen- and estrogen-receptor content in spontaneous and experimentally induced canine prostatic hyperplasia

To gain insight into the mechanism by which steroidal hormones influence the development of canine prostatic hyperplasia, nuclear and cytosolic androgen- and estrogen-receptor content, as measured under exchange conditions by the binding of [(3)H]R1881 (methyltrienolone) and [(3)H]estradiol, respectively, were quantitated in the prostates of purebred beagles of known age. In young dogs with spontaneously arising and experimentally induced (androstanediol plus estradiol treatment) prostatic hyperplasia, nuclear, but not cytosolic, prostatic androgen-receptor content was significantly greater than that determined in the normal prostates of age-matched dogs (3,452+/-222 and 4,035+/-274 fmol/mg DNA vs. 2,096+/-364 fmol/mg DNA, respectively). No differences were observed between the androgen-receptor content of the normal prostates of young dogs and the hyperplastic prostates of old dogs. The cytosolic and nuclear estrogen-receptor content of spontaneously arising prostatic hyperplasia in both young and old animals was similar to that found in normal prostates. The administration of estradiol plus androstanediol to castrate dogs significantly increased the prostatic nuclear androgen-receptor content over that found in dogs treated only with androstanediol. This estradiol-associated increase in nuclear androgen-receptor content was accompanied by the development of benign prostatic hyperplasia. Estradiol treatment of castrate dogs resulted in an increase in prostatic nuclear estrogen-receptor content, in the appearance of a putative prostatic cytosolic progesterone receptor, and in an alteration of the epithelium of the prostate to one characterized by squamous metaplasia. Treatment of castrate dogs with both estradiol and androstanediol resulted in a reduction in prostatic nuclear estrogen-receptor content, disappearance of the progesterone receptor, and loss of squamous metaplasia. An increase in nuclear androgen-receptor content, thus, appears to be an important event in the development of both spontaneously arising and experimentally induced canine prostatic hyperplasia. The mechanism of androgen-estrogen synergism in the experimental induction of canine benign prostatic hyperplasia may be explained by estradiol-mediated increases in nuclear androgen-receptor content. Because androstanediol blocked certain estradiol-mediated events within the prostate, a negative feedback mechanism may exist in which the response of the canine prostate to estrogens is modulated by rising levels of androgen.

Age-related changes in the prostate and testes of the beagle dog

Age-related changes in the histologic morphology of the Beagle dog prostate have been used as a model for similar changes that occur in human beings. Previous studies of the aging changes in Beagle dogs have been limited to animals less than 10 years of age. In this study, the prostate, testes, and serum testosterone levels were evaluated in healthy Beagle dogs that were grouped by age to provide five groups of dogs that ranged from 3 to 14 years of age. Tissue sections from the prostate and testes were examined qualitatively and quantitatively by light microscopy. All animals 6 years of age and older had histologic characteristics of complex benign prostatic hyperplasia. A mean statistically significant increase in prostatic weight with increased age was noted (mean value 1.08 +/- 0.22 g/kg body weight at 3 years of age, increasing to 2.64 +/- 0.37 g/kg body weight at 14 years of age). Morphometric analysis of the prostatic tissue suggested that similar to the change observed in human males, the increase in size was primarily due to an increase in the absolute volume of interstitial tissues (mean value 2.8 +/- 1.1 cm3 at 3 years of age, increasing to 7.4 +/- 1.3 cm3 at 14 years of age). The epithelial component did not contribute to the increase noted, with the exception that the percentage of glandular lumen did increase with age, indicating progressive cystic dilatation of the glands.(ABSTRACT TRUNCATED AT 250 WORDS)

Concentration of dihydrotestosterone and 3 alpha-androstanediol in naturally occurring and androgen-induced prostatic hyperplasia in the dog

Previous studies have suggested that dihydrotestosterone accumulation in the prostate may be involved in the pathogenesis of prostatic hyperplasia in man and dog. However, the fact that the administration of 10 mg dihydrotestosterone/d to castrated, mongrel dogs (0.5 mg/kg body wt) causes little growth in the prostate, whereas identical doses of 3alpha- androstanediol regularly induce prostatic hyperplasia (> 14 g weight) has raised the possibility that the dihydrotestosterone accumulation may be the result rather than the cause of the pathology. To investigate the mechanism of this phenomenon, we measured the levels of dihydrotestosterone and 3alpha-androstanediol in prostates from 75 dogs. In both naturally occurring and 3alpha-androstanediol-induced prostatic hyperplasia, the levels of dihydrotestosterone were high (>5 ng/g), whereas in immature glands and glands from dihydrotestosterone-treated animals, levels were similar (2.1 and 2.6 ng/g, respectively). 3alpha-Androstanediol levels were no different in animals treated with dihydrotestosterone or 3alpha-androstanediol.Therefore, because exogenous 3alpha-androstanediol is a better precursor of prostatic dihydrotestosterone than exogenous dihydrotestosterone itself, the effects of treatment with larger doses (2.5 mg/kg per d) of dihydrotestosterone and 3alpha-androstanediol for 12 wk were examined. In these amounts, dihydrotestosterone was as effective as 3alpha-androstanediol in inducing the development of prostatic hyperplasia and in elevating prostatic dihydrotestosterone concentration. Because dihydrotestosterone accumulates in spontaneous prostatic hyperplasia, because the administration of sufficient amounts of dihydrotestosterone to the castrated dog can induce the development of prostatic hyperplasia, and because 3alpha-androstanediol induces the development of hyperplasia via conversion to dihydrotestosterone, we conclude that accumulation of dihydrotestosterone is the cause of canine prostatic hyperplasia.

Influence of orchiectomy on canine behaviour

One hundred and twenty-two dog owners were interviewed to obtain information about the effects of orchiectomy on the behaviour, unwanted side effects, and testosterone-dependent disease processes in their dogs. Behavioural problems were the main reason for orchiectomy, unwanted sexual behaviour being the most common, together with roaming, aggression, and abnormal urination behaviour. Objectionable sexual behaviour, inter-male aggression, roaming, and abnormalurination were reduced after orchiectomy in approximately 60 per cent of the dogs. The side effects of orchiectomy included increased bodyweight, increased appetite and decreased activity in less than 50 per cent of the dogs, and there was a significant relationship between increased appetite and bodyweight. The clinical signs of testosterone-dependent disease in most of the dogs either decreased or disappeared after orchiectomy.

Evaluation of serum and seminal plasma markers in the diagnosis of canine prostatic disorders

Serum and seminal plasma concentrations or activities of acid phosphatase (AP), prostate specific antigen (PSA), and canine prostate specific esterase (CPSE) were measured in normal dogs, dogs with benign prostatic hyperplasia (BPH), dogs with bacterial prostatitis, and dogs with prostatic carcinoma to determine if these assays would be of value in differentiating dogs with prostatic carcinoma from normal dogs, and dogs with other prostatic disorders. In addition, tissue sections of prostatic adenocarcinomas were stained with antiprostatic AP, anti-CPSE, and anti-PSA antibodies to determine if these would be suitable immunohistochemical markers of prostatic carcinoma. Prostate-specific antigen was not detected in canine serum or seminal plasma. Serum and seminal AP activities did not differ significantly between normal dogs and those with prostatic diseases, or among dogs with different prostatic disorders. Serum CPSE activities were significantly higher in dogs with BPH than in normal dogs. Mean serum CPSE activities in dogs with BPH, bacterial prostatitis, and prostatic carcinoma were not significantly different from each other. Slight to moderate immunohistochemical staining of canine prostatic adenocarcinomas was noted for prostatic AP and PSA; most tumors did not stain for CPSE. These results show that proteins of prostatic origin appear in the serum of dogs as a result of prostatic pathology, especially BPH. Canine prostatic adenocarcinoma does not appear to be associated with significant increases in CPSE or AP activities, possibly because of down-regulation of these enzymes by prostatic carcinoma cells. It is also possible that failure to detect significant differences resulted from limited statistical power for some groups and pairwise analyses because of the small number of dogs evaluated.

Role of canine basal cells in postnatal prostatic development, induction of hyperplasia, and sex hormone-stimulated growth; and the ductal origin of carcinoma

BACKGROUND

The canine prostate has often been proposed as a model for abnormal growth of the human gland. Hyperplasia of the prostate is common in aging men and has been estimated to be present in 100% of old intact dogs. While prostatic carcinoma is common in older men, it appears to be rare in dogs and unlike the disease in humans, it occurs with relatively high frequency in castrated animals. Since basal cells are thought to be key participants in normal and abnormal growth of the human gland, we used immunohistochemistry to investigate the role that they may play in canine prostatic development, the evolution of hyperplasia and carcinoma, and the effects of sex hormones on these cells.

METHODS

Prostate specimens were obtained at autopsy from seven sexually immature dogs, autopsy and biopsy samples from 14 sexually mature intact animals, from four castrates, and from19 dogs with prostatic carcinoma. In addition, we also studied the prostates from two intact dogs treated with 5alpha-dihydrotestosterone (DHT) for 6 months and two castrated dogs that were subsequently treated with 5alpha-androstane-3alpha diol and estradiol-17alpha, as well as specimens from two sexually ablated animals given DHT for 2 weeks. All specimens were immunostained for high molecular weight cytokeratin (HMC), pancytokeratin, androgen receptor (AR), and the proliferative marker KI-67.

RESULTS

We find that basal cells are the major proliferative cell type in the neonatal and adult canine prostate and that the expression of HMC staining, which defines these cells, may be regulated by androgens. In the adult gland, ductal basal cells formed a contiguous layer, whereas those lining acini were discontinuous. Populations of both basal cell types were variably AR positive, but while HMC immunostaining was abolished in acinar cells following long-term castration, staining remained in ductal cell counterparts. Paralleling the histological development of hyperplasia, the acinar basal cell population increased with age and were the major cell type that expressed KI-67. In contrast, ductal basal cell populations did not expand in the prostates of older dogs and were seldom positively stained for KI-67. The numbers of HMC and KI-67-stained acinar basal cells were dramatically increased in the prostates of intact dogs treated with DHT when compared with glands of untreated controls. This was not the case with ductal basal cells. Androgens given alone or together with estrogen to castrated dogs induced widespread HMC and KI-67 immunostaining in both populations of basal cells. In addition, our results indicate that the majority of canine prostatic carcinomas likely arise exclusively from ductal epithelium. Only one of the 19 cases of carcinoma contained cells that expressed AR, which suggests that androgens may not be required for the initiation or progression of these cancers.

CONCLUSIONS

Our findings indicate that two biologically distinct populations of basal cells may exist in the canine prostate. In this regard, the age-related expansion of proliferating acinar basal cell populations, probably mediated by sex steroids, is a key factor in the pathogenesis of canine prostatic hyperplasia. Additionally, we find that prostatic carcinoma in the dog likely arises from ductal cells. Taken together, these findings may indicate that canine acinar basal cells and ductal epithelium have separate susceptibilities to factors that promote hyperplastic or neoplastic development.

Effects of finasteride on size of the prostate gland and semen quality in dogs with benign prostatic hypertrophy

OBJECTIVE

To determine the effect of the 5alpha-reductase inhibitor finasteride on prostatic diameter and volume, semen quality, and serum dihydrotestosterone (DHT) and testosterone concentrations in dogs with spontaneous benign prostatic hypertrophy (BPH).

DESIGN

Double-blind placebo-controlled trial.

ANIMALS

9 dogs with BPH.

PROCEDURE

Five dogs were treated with finasteride for 16 weeks (0.1 to 0.5 mg/kg [0.05 to 0.23 mg/lb] of body weight, PO, q 24 h); the other 4 received a placebo. Prostatic diameter, measured radiographically, prostatic volume, measured ultrasonographically, semen quality, and serum DHT and testosterone concentrations were evaluated before and during treatment. After receiving the placebo for 16 weeks, the 4 control dogs were treated with finasteride for 16 weeks, and evaluations were repeated.

RESULTS

Finasteride significantly decreased prostatic diameter (mean percentage decrease, 20%), prostatic volume (mean percentage decrease, 43%), and serum DHT concentration (mean percentage decrease, 58%). Finasteride decreased semen volume but did not adversely effect semen quality or serum testosterone concentration. No adverse effects were reported by owners of dogs in the study.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggest that finasteride can be used to reduce prostatic size in dogs with BPH without adversely affecting semen quality or serum testosterone concentration.

A retrospective analysis of 111 canine prostatic samples: histopathological findings and classification

The purpose of this retrospective study is to evaluate the frequency and further characterize the pathological features of common and uncommon histological lesions in 111 canine prostatic samples. Benign prostatic hyperplasia, suppurative and non-suppurative prostatitis, and prostate cancer were observed individually or in combination in 45, 11, 68 and 50 samples, respectively. Six growth patterns of prostatic carcinoma were differentiated: papillary, cribriform, solid, small acinar/ductal, signet ring, mucinous. In a few cases, perineurial invasion and collagenous micronodules were observed. Lesions considered preneoplastic in men, such as high-grade prostatic intraepithelial neoplasia (HGPIN) and prostatic inflammatory atrophy (PIA), were observed in 27 and 21 histological samples, respectively. This study represents a detailed characterization of the different histological subtypes of canine prostate cancer. The awareness of the unusual patterns might be critical in avoiding diagnostic misinterpretation. The high prevalence of PIA and HGPIN underlines the reasonable chance of their detection in routine biopsy specimens.

Ultrasonographic estimation of prostatic size in canine cadavers

The purpose of this study was to determine the accuracy of transabdominal ultrasound in estimating the volume and weight of the canine prostate gland, to derive a simple formula from actual and ultrasonographic prostate measurements for estimating prostate volume and weight, and to evaluate the reproducibility of ultrasonographic measurements of linear prostate dimensions. The prostate volume and weight were measured and also calculated in 77 male canine cadavers (60 entire and 17 neutered) with the aid of statistical computer programmes using actual linear dimensions of the prostate ('actual') and those measured ultrasonographically before ('in vivo') and after ('in vitro') removal of the prostate gland. Therefore, 'in vivo', 'in vitro' and 'actual' estimations of prostate size were obtained and compared with prostatic volume and weight. The evaluation of the reproducibility of the ultrasonographic measurements made was performed in 59 of the dogs in which the prostate was imaged three times in longitudinal and three times in transverse sections. This study demonstrated that prostatic weight and volume are related to body weight and age in entire dogs but not in neutered dogs. Formulae were derived to estimate prostate weight and volume from physical and ultrasonographic measurements. There were good correlations between the ultrasonographic and physical measurements and prostate size derived from these measurements provided a good estimate of actual prostate size. 'Best subsets' analyses indicated that prostate width and length (measured physically or ultrasonographically) were the best predictors of prostatic volume and weight, both when all dogs were considered together and in entire dogs only. Statistical analyses indicated that there were no significant differences between the repeated measurements of length and depth (P>0.05). However, there was a significant difference between repeated measurements of width (P= 0.0357).

Quantitative changes in the morphology of the aging canine prostate

Stereological methods at the light and electron microscopic levels were used to examine the morphological changes in the beagle prostate associated with increasing age and with the occurrence of spontaneous benign hyperplasia. Analyses of semithin sections of tissue embedded in plastic revealed that proliferation of prostatic glandular and stromal components, increase in epithelial cell numbers, and increase in epithelial cell size all contributed to the dramatic increase in prostate weight seen in aging dogs. Analyses at the electron microscopic level revealed that the volume densities of rough endoplasmic reticulum and secretion granules were significantly lower in epithelial cells of the immature prostate than in the prostate of mature dogs (greater than 1.5 years of age). In contrast, no significant differences were seen in the volume densities of rough endoplasmic reticulum, free ribosomes, secretion granules, smooth endoplasmic reticulum, or mitochondria in randomly selected prostatic epithelial cells of dogs 1.5 to 9 years of age, whether or not the prostates were hyperplastic.

Histopathological Terminology Standards for the Reporting of Prostatic Epithelial Lesions in Dogs

The terminology applied to canine prostatic epithelial lesions, especially carcinomas, is currently not standardized and this hampers the ability of pathologists to study the biological and clinical significance of these lesions. The aim of this review is to present the essential histomorphological diagnostic attributes of a wide spectrum of prostatic epithelial lesions in dogs. In addition to the traditionally recognized prostatic hyperplasia, hormonal atrophy, prostatitis, squamous metaplasia, adenocarcinoma and transitional cell (urothelial) carcinoma, new entities are described and discussed in order to provide veterinary pathologists with a basic atlas of common histological lesions of the canine prostate that is comprehensive and easy to use.

Progressive prostate hyperplasia in adult prolactin transgenic mice is not dependent on elevated serum androgen levels

BACKGROUND

Transgenic mice overexpressing the rat prolactin (PRL) gene under control of the metallothionein-1 promoter (Mt-1) develop a dramatic prostatic enlargement. These animals also display significantly elevated testosterone serum levels. In this study, we aim to clarify the role of circulating androgen levels in the promotion of abnormal prostate growth in the adult PRL transgenic mouse prostate.

METHODS

Prostate morphology and androgen-receptor distribution patterns were analyzed in castrated and testosterone substituted adult PRL transgenic and in wild-type males.

RESULTS

Progressive prostatic hyperplasia in adult PRL transgenic males was not affected by substitution to serum testosterone levels corresponding to wild-type. Furthermore, prolonged testosterone treatment in adult wild-type males did not produce any significant changes in prostate growth or morphology compared with wild-type controls. Immunohistochemical studies revealed a significantly increased proportion of androgen receptor positive epithelial cells in all lobes of the PRL transgenic prostate versus wild-type.

CONCLUSION

The present study demonstrates that progressive prostate hyperplasia in adult PRL transgenic mice is not dependent on elevated serum androgen levels. Furthermore, prolonged androgen treatment in adult wild-type male mice appears to have no significant effect on prostate growth. In addition, our results suggest that prolonged hyperprolactinemia results in changes in prostate epithelial and stromal cell androgen receptor distribution.

Effect of tamoxifen citrate on reproductive parameters of male dogs

Tamoxifen is a synthetic, nonsteroidal Type I antiestrogenic compound that competitively blocks estrogen receptors with a mixed antagonist-agonist effect. The manifestation of these different actions depends on each species, organ, tissue and cell type considered. Very little is known about the effect of antiestrogens in dogs. The objectives of this study were to determine the effects of tamoxifen citrate on some testis, prostate, hormone, and semen parameters in seven Beagle dogs with uncomplicated spontaneous benign prostatic hyperplasia. Two dogs were normospermic, four were oligozoospermic, and one was azoospermic. The dogs were allocated to a control pre-treatment period, followed by a treatment period, and five post-treatment periods (the duration of each period was 4 weeks). During the treatment period, 2.5mg tamoxifen citrate was given p.o. daily for 28 days to all the dogs. Maximum scrotal width, testicular consistency, libido semen parameters, prostatic volume, serum testosterone concentrations, and side effects were assessed. Tamoxifen negatively affected testis size and libido (P<0.01), and decreased prostatic volume (P<0.01) and testosterone concentrations during treatment. Semen quality deteriorated to nadir values (P<0.01) approximately one spermatic cycle after treatment and returned to pre-treatment values on the second cycle after treatment in all the dogs, except one young oligoazoospermic dog, in which the sperm count was higher ( P<0.01 ) at that time. No side effects were observed and fertility was conserved at the end of the study. Tamoxifen acted more like an agonist than antagonist on the gonadal axis and, therefore, upon both the prostate and testis. Therefore, tamoxifen may have therapeutic applications in dogs.

Expression of androgen, oestrogen alpha and beta, and progesterone receptors in the canine prostate: differences between normal, inflamed, hyperplastic and neoplastic glands

The expression of receptor for androgen (AR), oestrogen alpha and beta (ERalpha and ERbeta) and progesterone (PR) was examined immunohistochemically in canine prostate specimens (normal, hyperplastic, inflamed [prostatitis] or neoplastic). AR immunolabelling was seen in 100% of epithelial cells of normal and hyperplastic tissue, the corresponding figures for inflamed and carcinomatous tissue being 74% and 65%, respectively. ERalpha labelling was seen in 85% of epithelial cells in normal prostate glands, the corresponding figures for hyperplastic, inflamed and neoplastic glands being 35%, 22% and 12%, respectively. ERbeta labelling was seen in 85% of epithelial cells of normal glands and in about 70% of such cells in glands showing pathological changes. On the other hand, PR expression (weak) in normal glands was observed in fewer epithelial cells (44%) than in hyperplastic (70%), inflamed (62%) or neoplastic (64%) glands.

Magnetic resonance imaging of the efficacy of specific inhibition of 5 alpha-reductase in canine spontaneous benign prostatic hyperplasia

A leading role for prostatic levels of dihydrotestosterone (DHT) in the pathogenesis of benign prostatic hyperplasia is well established, if incompletely understood. The present study provides initial confirmation that 5 alpha-reductase inhibition alone is sufficient to prevent prostatic accumulation of DHT and to produce epithelial regression in the canine prostate. In dogs treated with the specific 5 alpha-reductase inhibitor finasteride, prostatic volume decreased to one-third of the baseline volume, while the prostatic concentration of DHT fell fivefold: both were constant in placebo control dogs. Demonstration that MR imaging can serve as accurate modality to assess prostatic volume was provided by serial measurements of the canine prostate and by correlation of the last imaging measurement with the weight of the excised prostate. Significant intensity changes were observed in T2-weighted images measured post-treatment; these changes correlated with the histopathology of the prostate. These results suggest that beyond quantifying regression, multiecho T2 measurements can be useful in probing accompanying changes occurring on the cellular level.

Effect of osaterone acetate administration on prostatic regression rate, peripheral blood hormone levels and semen quality in dogs with benign prostatic hypertrophy

The effects of osaterone acetate (OSA), which is an anti-androgen agent being developed as a therapeutic drug for benign prostatic hypertrophy (BPH) in dogs, on the degree of prostatic regression and semen qualities were investigated. Prostatic regression was compared between dogs with and without orchidectomy. Five male beagles aged 5-9 years were used in the experiment. OSA was orally administered at doses of 0.2 mg/kg and 0.5 mg/kg for one week. The prostatic regression rate one week after the end of administration was 62.6% on average. In the orchidectomized group, the mean regression rate one week after orchidectomy was 60.1%. However, the prostate became enlarged 6 months after administration, compared to the size prior to administration. The above findings suggested that OSA is clinically applicable as a therapeutic drug for BPH in dogs, and inhibits prostatic hypertrophy during the early phase.

Testicular androgen and estrogen secretion and benign prostatic hyperplasia in the beagle

The natural history of benign prostatic hyperplasia (BPH) in the dog is characterized by a slow progression through two phases. The early phase of the disease process is characterized by glandular hyperplasia and occurs as early as 2.5 yr of age. The late phase of the disease is characterized by cystic hyperplasia and occurs after 4 yr. The results of the present study are the first to compare Leydig cell structure and steroidogenic function in dogs with BPH with those in age-matched controls. It was discovered that glandular BPH can occur in young dogs (2.5 yr) in which Leydig cell mass and ultrastructure and maximally stimulated androgen secretion are indistinguishable from those in age-matched controls. These results support the concept that the early phase of BPH (glandular hyperplasia) is not related temporally to some defect in the Leydig cell. In contrast, the late phase of BPH (cystic hyperplasia) in beagles 6 yr of age is associated with diminished smooth endoplasmic reticulum in the Leydig cell and with diminished production of androgens by perfused testes in vitro. During the course of these studies, we discovered that the testes of young beagles with BPH, but not age-matched controls or old beagles with BPH, secrete an unidentified molecule (putative estrogen). This molecule was characterized partially in that it is extractable from testicular venous effluent with diethyl ether, elutes in a discrete fraction in several different high performance liquid chromatographic systems, reacts with an antibody that recognizes 17 beta-estradiol, estrone, and estriol, and competes with 17 beta-[3H]estradiol for the rat uterine estrogen receptor. Based on the elution volume from high performance liquid chromatography, the unknown molecule (putative estrogen) is not estriol, estradiol, or estrone.

Characterization of prostatic basal cell hyperplasia and neoplasia in aged macaques: comparative pathology in human and nonhuman primates

There are very few reports of proliferative prostatic lesions occurring spontaneously in nonhuman primates. We found that 15 of 19 glands in aged macaques contained one or more epithelial lesions in the cranial lobe. These originated in the basal cell compartment and were characterized as hyperplasia and benign neoplasia. The adenomas contained variable gland formation, with morphologic and immunohistochemical evidence of secretory, mucigenous, neuroendocrine, transitional, and squamous cell differentiation. These cell types are resident in the normal prostate or appear in metaplastic lesions, and their presence in the macaque tumors is consistent with differentiation of a stem cell along multiple phenotypic pathways. The macaque growths are similar to human prostatic basal cell lesions and could provide insights into their pathogenesis as well as cellular ontogeny and general mechanisms of carcinogenesis in this organ.

Urethral bleeding as a presenting sign of benign prostatic hyperplasia in the dog: a retrospective study (1979-1993)

Nineteen dogs were presented to the Murdoch University Veterinary Hospital (MUVH) because of blood loss from the urethra, unassociated with other clinical signs of prostatic disease. Blood loss was intermittent in all cases, but was severe enough to require blood transfusion in one case. Prostatic enlargement was detected on rectal palpation in all cases, and benign prostatic hyperplasia was diagnosed after elimination of other prostatic diseases (i.e., infection, cysts, neoplasia) using diagnostic imaging and clinical laboratory tests. Castration resulted in cessation of blood loss; whereas antiandrogen therapy, an alternative treatment to castration, was less effective.

Finasteride-induced prostatic involution by apoptosis in dogs with benign prostatic hypertrophy

OBJECTIVE

To determine the effect of finasteride on programmed cell death (apoptosis) of prostatic cells during prostatic involution in dogs with benign prostatic hypertrophy (BPH).

ANIMALS

9 dogs with BPH.

PROCEDURE

Dogs were randomly assigned to treatment or control groups. Treatment dogs (n = 5) were administered finasteride (0.1 to 0.5 mg/kg, PO, q 24 h) for 16 weeks, whereas the 4 control dogs were administered an inert compound. Prostatic cells from the prostatic fluid portion of the ejaculate of treatment and control dogs were obtained before and 1, 2, 3, 4, 8, and 16 weeks after initiation of treatment. Cells were concentrated by use of centrifugation. Prostatic cells were examined for indications of apoptosis by use of a terminal deoxyribonucleotidyl transferase-mediated deoxyuracil triphosphate nick-end labeling technique. After receiving the inert compound for 16 weeks, the 4 control dogs were administered finasteride for 16 weeks, and evaluations were repeated.

RESULTS

Percentage of apoptotic prostatic cells in ejaculated prostatic fluid of treatment dogs increased significantly (from 9% before treatment to 33, 31, 26, and 27% after 1, 2, 3, and 8 weeks of treatment, respectively). There was no significant change in percentage of apoptotic prostatic cells in the ejaculated prostatic fluid of control dogs.

CONCLUSIONS AND CLINICAL RELEVANCE

Finasteride-induced prostatic involution appears to be via apoptosis in dogs with BPH. Finasteride treatment of dogs with BPH causes prostatic involution by apoptosis rather than necrosis.