Effect of aromatase inhibitor, TZA-2209, on the prostate of androstenedione-treated castrated dogs: changes in prostate volume and histopathological findings

A novel nonsecosteroidal VDR agonist (CH5036249) exhibits efficacy in a spontaneous benign prostatic hyperplasia beagle model

To date, there have been no reports showing the efficacy of nonsecosteroidal vitamin D receptor (VDR) agonists in a benign prostatic hyperplasia (BPH) animal model. To examine the efficacy of CH5036249, a novel nonsecosteroidal VDR agonist, we orally administered the compound at 0.03 microg/kg to a beagle model with spontaneous BPH. Prostate volume was checked by rectal ultrasonic probe periodically during 11 months of administration and the prostate tissues histologically examined. CH5036249 inhibited prostate growth in two out of three dogs compared with vehicle-treated dogs. In the prostate specimens, substantial atrophy of the epithelium was observed in all dogs administered CH5036249. At the dose given, serum calcium levels slightly increased in the CH5036249-treated dogs but stayed within a normal range. We next examined the cell growth inhibition of CH5036249 using human prostate stromal cells and found the cell growth inhibitory activity of CH5036249 to be comparable to that of 1alpha,25(OH)2D3. The bioavailability from oral administration in rats was 95.1% with a t1/2 of 17.6 h. Both micro-AMES and micronucleus tests were negative. Although the results are still preliminary, we consider the novel nonsecosteroidal VDR agonist CH5036249 to be a possible new drug candidate for the treatment of BPH in humans.

Effects of mepartricin, a polyene macrolide antibiotic, on estrogen-induced hyperplastic growth of the dorsolateral prostate and seminal vesicle in immature castrated rats

OBJECTIVE

To investigate the effects of mepartricin, a polyene macrolide antibiotic, on estrogen-induced hyperplastic prostate and seminal vesicle (SV) growth in castrated rats.

MATERIAL AND METHODS

Immature rats aged 3 weeks were castrated and left untreated for 1 week. Then, 17beta-estradiol benzoate (E(2)-BA) was subcutaneously injected at a dose of 10 microg/day twice weekly, and mepartricin was orally administered at doses of 2.5, 5 and 10 mg/kg once daily for 3 weeks. The weights and hydroxyproline contents of the prostate and SV, the activity of growth factors (GFs) in the dorsolateral prostate (DLP) and the serum estrogen level were measured. Histological examination of the prostate and SV was also performed.

RESULTS

Mepartricin dose-dependently suppressed the increase in the serum estrogen level, the weights and hydroxyproline contents of the DLP and SV and the elevation of GF activity in the DLP induced by E(2)-BA treatment. Histological examination also revealed that treatment with mepartricin reduced collagen accumulation and thickening of the smooth muscle layer in the DLP and SV, and proliferation of the glandular epithelium in the DLP.

CONCLUSIONS

These results suggest that mepartricin suppresses hyperplastic growth of the DLP and SV induced by estrogen in immature castrated rats, the underlying mechanism being a reduction in the serum estrogen level, thereby suppressing stromal cell proliferation and activation.

Changes in the endocrine environment of the human prostate transition zone with aging: simultaneous quantitative analysis of prostatic sex steroids and comparison with human prostatic histological composition

BACKGROUND

It is well-known that the incidence of benign prostatic hyperplasia (BPH) increases with aging. The age-dependent changes in the ratio of serum sex steroid concentrations may play a role in BPH development. To clarify the relationship between the prostatic tissue concentrations of these steroids and age, we established a precise method of simultaneous quantitative analysis for prostatic sex steroids and used this method to investigate the tissue concentrations of three major sex steroids (testosterone, dihydrotestosterone, and estradiol) in the human prostate.

METHODS

The methodology for the simultaneous quantitative analysis of prostatic sex steroids was established using castrated rat prostatic tissue, coupled with internal standards, for androgen-deprived medium, and the validation of the method was examined. Human prostatic tissues were collected during surgery and immediately frozen at -70 degrees C. Using our method, the steroidal fractions were extracted, purified, and quantified. The proportions of stroma, epithelium, and glandular lumen were measured on each histological specimen, using an image analyzer.

RESULTS

The validation tests showed that our method of quantitative analysis was precise and sensitive enough for the quantification of testosterone, dihydrotestosterone, and estradiol in the prostate. In humans, the prostatic dihydrotestosterone concentration decreased with age, but the concentrations of testosterone and estradiol showed no relation with age. Therefore, the ratio of estradiol to dihydrotestosterone concentration (E2/DHT) in prostate increased with age. The E2/DHT ratio showed a significant positive correlation with the proportion of stroma.

CONCLUSIONS

The age-dependent decrease in prostatic dihydrotestosterone and constant estradiol concentration lead to a relatively estrogen-dominant environment compared to that at younger ages. We assume that this relatively estrogen-dominant status induces stromal proliferation by some mechanism and leads to the development of BPH.

Estimation of canine prostatic volume: nomogram based on prostatic cubic volume

To estimate prostate volume in canines, we demonstrated the nomogram based on prostatic cubic volume. Transrectal ultrasonography (TRUS) was performed in twenty beagle dogs. Prostatic length (L) and height (H) were determined on sagittal image, and prostatic width (W) was determined on transaxial image. Data of one dog, which had asymmetrical shaped prostate, were excluded from the analysis. Prostate volume was estimated by the following nomogram: Gravimetric prostatic volume (g) = 0.642 x prostatic cubic volume (cm3) + 1.84 (prostatic cubic volume = L x H x W cm3, r = 0.997, p<0.001). By substituting the prostatic height to the average of height, prostatic volume of one dog showing asymmetrical shape was successfully estimated. We also showed technical points in evaluating morphology of canine prostate on TRUS. In conclusion, this nomogram is of great use for directly estimating prostatic volume.

Effect of dual inhibition of 5-alpha-reductase and aromatase on spontaneously developed canine prostatic hypertrophy

BACKGROUND

Our aim was to assess the effect of dual inhibition of 5-alpha-reductase and aromatase on prostate glands.

METHODS

We investigated the morphological changes in the prostate gland and the changes in the hormonal environment after administration of finasteride and arimidex to intact canine specimens. The study consisted of four groups: a 5-alpha-reductase only group (5RI only, n = 5); a 5RI plus aromatase-inhibitor combination group (5RI + ARI combination, n = 5); a BPH control group (n = 3); and a castration control group (n = 3). Finasteride (1 mg/kg/day) and the same dose of arimidex were orally administered for 80 days.

RESULTS

In the 5RI group, a significant decrease in the serum dihydrotestosterone (DHT) level was found, and prostatic volume was significantly decreased. However, significant increases in serum testosterone (T) and DHT levels were observed, with a concomitant increase in prostatic volume in the 5RI + ARI combination group. Morphometric analysis showed that histopathological findings in the 5RI + ARI combination group were similar to those in the BPH control group.

CONCLUSIONS

Dual inhibition of 5-alpha-reductase and aromatase resulted in a significant increase in prostate volume, accompanied by a 3-10-fold increase in serum testosterone levels and a significant increase in testicular volume.