Castrated Dogs Research Articles

Antispermatogenic/antiandrogenic properties of solasodine (C27H43O2N) obtained from solanum xanthocarpum berries on the male genital tract of dog (Canis-familiaris). A histophysiological approach.

Chronic administration of solasodine (20 mg/kg alt. day for 30 days) caused testicular lesions resulting in a severe impairment of spermatogenic elements. The epididymides were devoid of spermatozoa. Total protein, sialic acid and glycogen contents of the testis and epididymis were reduced significantly whereas the testicular cholesterol was elevated. Acid Phosphatase enzyme activity of the testes was low after solasodine treatment. Serum enzymes (SGPT, alkaline phosphatase) serum protein, triglycerides, non esterified fatty acid levels were in normal range when compared with their own controls. Cholesterol and phospholipid levels were elevated after solasodine treatment to intact dogs. Reduced androgen production was reflected in low levels of sialic acid in the testes and epididymides and reduced Leydig cell nuclei. Castration alone brought about reduction in size of the epididymis. Castration followed by solasodine treatment caused epididymal degeneration. Simultaneous administration of TP to solasodine treated castrated dogs failed to stimulate the epididymal growth. Antispermatogenic/antiandrogenic activity of the compound solasodine is discussed. Solasodine administration in dogs definitely rendered the male infertile as evidenced by the absence of sperms in the cauda epididymis and ductus deferens.

Effects of the administration of androgenic and estrogenic steroids on 3α-hydroxysteroid dehydrogenase levels of the intact and castrated dog prostate

The 3α-hydroxysteroid dehydrogenase activity of dog prostate microsomes has been measured by monitoring the NADH-dependent reduction of dihydrotestosterone (17β-hydroxy-5α-androstan-3-one) to 5α-androstane-3α,17β-diol by a novel and highly sensitive enzymatic procedure. In confirmation of the work of others (e.g. G. H. Jacobi, R. J. Moore and J. D. Wilson, Endocrinology 102 (1978) 1748–1755) we have found that 3α-hydroxysteroid dehydrogenase falls to negligible levels after castration. Treatment with estradiol-17β has no effect on the low enzyme activity found in prostate microsomes of castrated dogs, but reduces this activity in intact animals to less than 10% of control values. The specific activities of 3α-hydroxysteroid dehydrogenase of castrated dogs can be restored to 50–100% of control levels by treatment with testosterone, dihydrotestosterone or 5α-androstane-3α,17β-diol. These androgen-induced elevations of the enzyme are antagonized by the simultaneous administration of estradiol-17β. Contrary to the findings of others (G. H. Jacobi and J. D. Wilson, Endocrinology 99 (1976) 602–610) we could detect no correlation between the specific activities of 3α-hydroxysteroid dehydrogenase of prostate microsomes and the age of the animals, the size of their prostates or the presence of hyperplastic disease. In castrated beagles who have developed glandular prostatic hyperplasia in response to repetitive treatment with estradiol-17β in combination with either dihydrotestosterone or 5α-androstane-3α,17β-diol, the 3α-hydroxysteroid dehydrogenase specific activities are 26 and 44% respectively, of untreated controls. Although the capacity of dihydrotestosterone and 5α-androstane-3α,17β-diol to induce prostatic hyperplasia appears to be related to the ability of these steroids to elevate prostatic dihydrotestosterone levels (and the diol is more effective than dihydrotestosterone in doing so), the experimental production of this disease does not appear to require the presence of supernormal levels of 3α-hydroxysteroid dehydrogenase. Similarly, prostatic growth induced by treatment of intact beagles with the three above-mentioned androgens is not associated with elevations of 3α-hydroxysteroid dehydrogenase above normal.

Phenotypic modulation of the canine prostate after long-term treatment with androgens and estrogens.

Fine structural alterations of the canine prostate induced by long-term treatment of castrated adult animals with estrogens and/or androgens and also in combination with antiandrogens and/or antiestrogens for six months have been studied with particular respect to their topographic location within the gland. Three major patterns of structural responses of the epithelium have been distinguished: squamous metaplasia, atrophy, and hypertrophy, while in stroma, regression, hypertrophy, or sclerosis were observed. In addition to cellular alterations of stromal fibrocytes and smooth muscle cells, characteristic changes in the arrangement, distribution, and pattern of the different stromal elements occurred. General squamous metaplasia of the epithelium and regressive alterations of stromal cells were most obvious in animals treated with estradiol plus androstanediol. Atrophy of the epithelium and stromal sclerosis were the salient features of antiandrogen-treated castrated animals, while hypertrophy or hyperplasia of both the epithelium and stroma was a major finding in androstanediol-substituted castrated animals. Combined treatment caused rather heterogeneous structural patterns seemingly dependent on the location within the gland. The results indicate that the prostatic epithelial cells dispose of a broad variety of structural reaction patterns that, in case of combined hormonal treatment, are expressed in a manner typical for their locations within the ductal system of the gland. However, with the exception of combined treatment with estradiol, tamoxifen, and androstanediol of castrated dogs, none of the experimental protocols used induced a morphologic response of the gland comparable to that seen in human benign prostatic hyperplasia. The canine prostate therefore is of rather limited value as a model for human BPH.

The effect of oestrogen on stromal growth of the dog prostate: a quantitative ultrastructural study.

The stromal tissue of the prostate in normal castrated dogs and castrated and oestrogen treated dogs were studied by quantitative morphological methods. Quantitative morphological (=stereological) procedures provide values of volume, surface and number of tissue and cell components. The stereological data show an activation of the smooth muscle cell of the stromal tissue in the oestrogen treated dog compared with the control group; related to the unit volume of smooth muscle cell cytoplasm, a threefold increase of the endoplasmic reticulum was observed in castrated and oestrogen treated dogs.

Failure of prolactin infusion to elicit adrenal androgen secretion.

In order to test the theory that prolactin (Prl) regulates adrenal androgen (AA) secretion, large doses of bovine Prl were acutely infused into castrated dogs, and similar studies were performed with ovine Prl in castrated sheep. Prl with low-dose ACTH stimulation did not cause AA secretion beyond that which occurred following ACTH stimulation alone, and Prl alone did not stimulate AA secretion in vivo.

Characterization of canine prostatic cells from normal and hyperplastic glands

Secretory and non-secretory epithelial cells and fibroblasts obtained from normal and hyperplastic canine prostate glands and from prostates of 6-week castrated dogs are cultured in monolayers. Prostatic fibroblasts are grown in non-selective culture medium and found at densities of 1.040–1,045 g/ml in Percoll gradients. Enriched populations of each epithelial cell type are obtained by varying the duration of the culture combined with the use of selective MEM D-Val mixture. When separated by centrifugation in Percoll density gradients, the secretory cells (high A.P.) are found at densities of 1.02–1.03 g/ml whereas the non-secretory cells (low A.P.) have densities of 1.05–1.06 g/ml. Both epithelial cell types are present in the normal and hyperplastic glands at the time of explantation. There is no correlation between the prostatic weight and the proportion of each cell type present in the tissue. On the basis of cell density in Percoll gradients and A.P. activity, those prostates with a high percentage of non-secretory epithelial cells yield better attachment and overall cultures than glands consisting mainly of secretory cells. Our results strongly suggest that non-secretory cells are precursors of the secretory type. In addition, the cells involved in the aging process of the culture are the secretory epithelial cells.

Testosterone Regulation of Follicle‐stimulating Hormone Secretion in the Male Dog

Studies were carried put to determine the effect of various numbers of testosterone‐filied polydimethylsiloxane (PDS) capsules on plasma concentrations of testosterone and FSH in acutely orchidectomized dogs. Dogs were implanted with either one empty PDS capsule or one, three, or five testosterone‐filled PDS capsules. Blood samples were collected daily prior to implantation, following implantation, following castration, with capsules left in situ, and following capsule removal. Replacement of testosterone, using one testosterone‐filled capsule, did not prevent the postcastration rise of FSH. Replacement of testosterone, using three and five testosterone‐filled capsules, maintained both FSH and testosterone in castrated dogs at concentrations similar to those observed in intact animals. Removal of testosterone‐filled capsules from castrated dogs resulted in hypersecretion of FSH. These studies indicate that testosterone replacement within physiologic limits will maintain FSH in the acutely orchidectomized dogs at concentrations similar to those observed in intact, untreated animals.

Evidence for Existence of Cortical Androgen-Stimulating Hormone

An animal model using dexamethosone-suppressed, castrated dogs was developed to test the hypothesis that a pituitary hormone other than ACTH modulates adrenal androgen (AA) secretion. Plasma samples were obtained every 15 min during infusions of saline, synthetic alpha 1-24 corticotropin, porcine 1-39 corticotropin (ACTH), or bovine pituitary gland extract (PE) in a wide range of doses. Androstenedione (A), dehydroepiandrosterone (DHA), and cortisol (F) were quantified by radioimmunoassay. When the ratio of AA levels was related to those of F, in order to correct for ACTH content in the PE, the slopes of the dose-response curves for corticotropin and PE were different at the 0.01 level. For A the dose-response slope for the PE was 0.18 +/- 0.5 SE, whereas that of ACTH was 0.02 +/- 0.01. For the DHA response the slopes were 0.17 +/- 0.04 for the PE and 0.04 +/- 0.03 for ACTH. Related studies showed no increase in AA levels in response to luteinizing hormone-releasing hormone, bovine growth hormone (GH), bovine prolactin, ovine thyroid-stimulating hormone (TSH), or synthetic aqueous arginine vasopressin (AVP). We conclude that a pituitary factor other than ACTH, prolactin, GH, luteinizing hormone, follicle-stimulating hormone, TSH, or AVP may be responsible for the observed increase in AA concentrations.

The Dog Prostate Under Defined Hormonal Influences: An Approach to Experimental Induced Prostatic Growth

The prostate of castrated dogs following treatment with testosterone, dihydrotestosterone and androstanediol combined with 17-beta-estradiol application was analyzed by light microscopic stereology. In all three groups there is a statistically significant increase of prostatic volume and weight. There is a statistically significant increase of the relative and absolute volume of the glandular as well as of the stromal part. Seen by the absolute data there is only a statistically significant increase of the volumetric amount of the smooth muscle cells in the dihydrotestosterone and 17-beta-estradiol treated animals. Regarding tissue distribution there is no difference between the controls and the castrated testosterone and 17-beta-estradiol treated animals. Regarding the stromal part, there is no statistically significant difference between the testosterone and 17-beta-estradiol treated group and the control animals. TIn the androstanediol and 17-beta-estradiol group there is a double and in the dihydrotestosterone and 17-beta-estradiol group a four-fold increase of the stromal part. The synergistic effect of estrogens and androgens on the growth of both parts of the dog prostate--the glandular and stromal compartment--is discussed.

Role of the pituitary gland in experimental hormonal induction and prevention of benign prostatic hyperplasia in the dog.

The antiandrogen, cyproterone acetate (CPA), prevents development of prostatic hyperplasia, induced in castrated dogs by a 6 month-treatment with 5 alpha-androstane-3 alpha, 17 beta-diol (A)alone or in combination with 17 beta-oestradiol (E2). The immunoperoxidase technique was used to study functional cell types in the pars distalis of the pituitary gland and to detect growth hormone (GH) and prolactin (PRL) target sites in the prostate gland. Homologous radioimmunoassays for estimation of serum canine GH and PRL concentrations were also performed. Treatment with the combinations A + E2 and A + E2 + CPA resulted in morphological indications of stimulated GH and PRL cells and depressed gonadotrophs. This correlates well with an increase in PRL-dependent staining in glandular epithelium and fibromuscular tissue of the prostate gland. However, basal serum PRL and GH levels were not significantly affected. Treatment with A and A + E2 stimulated, while additional treatment with CPA clearly suppressed adrenocorticotrophin/melanotrophin (ACTH/MSH) cells. These findings indicate that an endocrine imbalance in hypothalamic-pituitary-adrenal function may be involved in induction and prevention of prostatic hyperplasia in the dog.

Testosterone Regulation of Luteinizing Hormone Secretion in the Male Dog

In the first experiment, plasma levels of testosterone (T) and LH were determined in male mongrel dogs following castration. Blood samples were collected every 4 h for 48 h and daily from days 3–12 post‐castration. Plasma T concentrations became undetectable by 8 h post‐castration, and remained undetectable until the end of the study. Plasma LH concentrations were undetectable for 16–20 h post‐castration, but increased to 4.5 ng/ml by 24 h. By 48 h, post‐castration, the LH reached 12.5 ng/ml, similar to levels reported previously in the castrated male dog.In a second experiment, studies were carried out to determine the effect of various numbers of T‐filled polydimethylsiloxane (PDS) capsules on plasma concentrations of T and LH in castrated male dogs. Dogs were implanted with either 1 empty PDS capsule or 1, 3, or 5 T‐filled PDS capsules. Blood samples were collected daily prior to implantation, following implantation, following castration, with capsules left in situ and following capsule removal. Replacement of T, using one T‐filled capsule, did not prevent the post‐castration rise of LH. Replacement of T. using 3 and 5 T‐filled capsules, maintained intact concentrations of both LH and T in castrated dogs. Removal of capsules from castrated dogs resulted in hypersecretion of LH similar to that observed in the first experiment. These studies indicate that T replacement within physiological limits will maintain LH in the castrated male dog at concentrations similar to those observed in the intact, untreated animal.

Evidence for existence of cortical androgen-stimulating hormone.

An animal model using dexamethosone-suppressed, castrated dogs was developed to test the hypothesis that a pituitary hormone other than ACTH modulates adrenal androgen (AA) secretion. Plasma samples were obtained every 15 min during infusions of saline, synthetic alpha 1-24 corticotropin, porcine 1-39 corticotropin (ACTH), or bovine pituitary gland extract (PE) in a wide range of doses. Androstenedione (A), dehydroepiandrosterone (DHA), and cortisol (F) were quantified by radioimmunoassay. When the ratio of AA levels was related to those of F, in order to correct for ACTH content in the PE, the slopes of the dose-response curves for corticotropin and PE were different at the 0.01 level. For A the dose-response slope for the PE was 0.18 +/- 0.5 SE, whereas that of ACTH was 0.02 +/- 0.01. For the DHA response the slopes were 0.17 +/- 0.04 for the PE and 0.04 +/- 0.03 for ACTH. Related studies showed no increase in AA levels in response to luteinizing hormone-releasing hormone, bovine growth hormone (GH), bovine prolactin, ovine thyroid-stimulating hormone (TSH), or synthetic aqueous arginine vasopressin (AVP). We conclude that a pituitary factor other than ACTH, prolactin, GH, luteinizing hormone, follicle-stimulating hormone, TSH, or AVP may be responsible for the observed increase in AA concentrations.

Estradiol and progesterone receptors in dog prostate cytosol

When intact or castrated dog prostate cytosol is incubated with tritiated estradiol, high levels of saturable binding can be observed in the 3–4S region of sucrose gradients. Occasionally a shoulder is also seen in the 8S region. The estradiol binding is specific for natural and synthetic estrogens. It is of high affinity ( K A = 2 × 10 9M −1). The binding component also has a relatively high affinity for 5α-androstane-3β,17β-diol, a major metabolite of 5α-dihydrotestosterone in dog prostate cytosol. Estradiol and 5α-androstane-3β,17β-diol can displace each other in competition experiments and they both yield identical concentration of sites by Scatchard analysis. The concentration of estradiol binding sites is quite variable in prostates from 24 h castrated dogs and no apparent correlation can be found between the concentration of sites and prostate wt. By contrast in the prostates from intact dogs there is a highly significant inverse relationship between prostate wt. and concentration of estradiol binding sites. The presence of progesterone receptors in dog prostate can also be demonstrated by sucrose density gradient analysis using the synthetic steroids R5020 (17,21-dimethyl-19-norpregna-4,9-diene-3,20-dione) and R1881 (17β-hydroxy-17α-methyl-estra-4,9,11-trien-3-one). The binding component sediments both in the 8S and 4S regions of sucrose gradients. It is present in low amounts under basal conditions. Five days after a single injection of estradiol valerate, the binding is increased about 10-fold. It is almost completely abolished by the addition of progesterone and various unlabeled synthetic progestins but only partly decreased by 5α-dihydrotestosterone. Relatively low and constant levels of progesterone receptors are observed in normal and hyperplastic prostates from adult dogs (30 ± 1 [S.E.M.] fmol/mg0. prot.)

Regulation of cytoplasmic dihydrotestosterone binding in dog prostate by 17 beta-estradiol.

17 beta-estradiol enchances androgen-induced prostate growth in the castrate dog to a degree comparable to that seen in spontaneous prostatic hypertrophy. To investigate the mechanism of this synergism, cytosol androgen binding was measured by a density gradient technique in prostates of control and 17 beta-estradiol-treated castrate dogs. [3H]Dihydrotestosterone was bound principally to a moiety that averaged 8.6S in size. Approximately twofold enhancement of this binding by 17 beta-estradiol was demonstrable after 1 wk of treatment with 750 microgram/wk and after 3 wk with 75 microgram/wk. Under conditions in which binding in the 8S region was demonstrable with dihydrotestosterone and testosterone no binding of 3 alpha-androstanediol or progesterone was detectable. Thus, enhancement by 17 beta-estradiol of a prostate cytosol androgen-binding protein occurs under circumstances in which 17 beta-estradiol enhances androgen-mediated prostatic growth.

Studies on the mechanism of 3 alpha-androstanediol-induced growth of the dog prostate.

The conditions under which dihydrotestosterone and 5 alpha-androstane-3 alpha, 17 beta-diol (3 alpha-androstanediol) induce prostatic growth in the castrate dog have been investigated in animals in which the initial size of the prostate was either normal or large. When androgen replacement was commenced immediately after castration of dogs with preexisting prostatic hypertrophy, dihydrotestosterone was as effective as 3 alpha-androstanediol in maintaining prostate weight. Under all other conditions examined (replacement commenced immediately after castration in dogs with small prostates or 2 weeks after castration in dogs with large prostates), 3 alpha-androstanediol but not dihydrotestosterone induced significant prostatic growth. The maximal effect of 3 alpha-androstanediol in inducing prostatic growth was observed in 12 weeks. The administration of 17 beta-estradiol enhanced the growth-promoting action of 3 alpha-androstanediol, but did not affect the action of dihydrotestosterone or influence 3 alpha-hydroxysteroid dehydrogenase activity in prostate. Thus, the synergistic effect of 17 beta-estradiol and 3 alpha-androstanediol seems to be independent of any effect on the interconversion of the two androgens. The activity of the 3 alpha-hydroxysteroid dehydrogenase in dog prostate was high under all conditions of accelerated prostatic growth and appeared to be under androgenic control.

Studies on the effect of 5α-androstane-3α, 17α-diol in the canine prostate [formula omitted

Adult beagle dogs, castrated one month previously, were treated with 5α-androstane-3α, 17α-diol (total dose 300 mg) over a period of one month. Examination of the prostate after treatment showed no significant change in size, weight or histological appearance from the castrate dog prostate. Subsequent administration of 5α-androstane-3α, 17β-diol (300 mg) over the same period of time resulted in restoration of the prostate size, weight and histological appearance to that of the normal intact dog prostate. It is concluded that exogenously administered 5α-androstane-3α, 17α-diol does not promote prostatic growth in the castrate beagle dog.

The induction of prostatic hypertrophy in the dog with androstanediol.

The effects of androstanediol and estradiol on prostatic growth were investigated in castrate dogs. Estrogens along resulted in no significant change in prostatic weight, whereas androstanediol produced growth comparable to that in uncastrated controls. Androstanediol plus estradiol resulted in an even more striking increase in prostate growth. Approximately half the animals receiving androstanediol alone and all of those receiving androstanediol plus estradiol fulfill the weight and histological criteria for prostatic hypertrophy in the dog. Since both these steroid hormones are presumed to be normal secretory products of the testis, it is possible that they are involved in the pathogenesis of prostatic hypertrophy in the dog.

Some aspects of androgen secretion by the canine adrenal.

The secretion of androgens by the adrenal cortex was studied in intact, castrated and hypophysectomized dogs. The secretory activity was determined by measuring total 17-oxosteroids in adrenal venous blood. Under sodium pentobarbital anesthesia, a, marked increase in the secretion of adrenal 17-oxosteroids was induced in intact and castrated dogs by an intravenous injection of adrenocorticotrophin (ACTH, 2iu/kg), the increase being sustained over a 2-hour period of observation. The secretory response to ACTH in castrated dogs seemed to be somewhat larger than that in intact ones. An intravenous injection of human chorionic gonadotrophin (HCG, 20iu/kg) to intact dogs failed to elicite notable secretion of the adrenal 17-oxosteroids. In other experiments, a treatment with methylenedianiline (15mg or 30mg/kg), an inhibitor of steroidogenesis. after injection of ACTH produced aa rapid diminution in adrenal 17-oxosteroid secretion in response to ACTH, the inhibition being observed within 15 minutes after the treatment. Furthermore, an intravenous injection of ACTH (2iu/kg) after pre-treatment with methylenedianiline (30mg/kg) to intact dogs failed to produce the increase of secretion. It is thus suggested that ACTH primarily produces an increase in secretion of the adrenal 17-oxosteroids and this effect is inhibited by a treatment with inethylenedianiline.

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.

Experimental studies on the effects in helminthic infection, with special reference to the gonadectomy of the host

Experimental studies on the effects in helminthic infection, with special reference to the gonadectomy of the host