Age-related Changes in the Prostate and Testes of the Beagle Dog

Abstract

Abstract. 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 f 0.22 g/kg body weight at 3 years of age, increasing to 2.64 k 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 k 1.1 cm3 at 3 years of age, increasing to 7.4 k 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. Stereologic analysis of the testes showed a decrease in the relative percentage of germ cells with increasing age (mean value 58.5 k 2.3% at 3 years of age, decreasing to 45.2 k 4.0% at 14 years of age). No distinct age-related trend was detected in serum testosterone concentrations. These findings indicate that the progression of benign prostatic hyperplasia occurs throughout the entire life span of the dog; an association with changes in the testes was not identified.

Models for studying benign prostatic hyperplasia

“…The onset of BPH in the dog may occur at as early as 2 ± 3 y of age, 61 but it occurs with high frequency in aged dogs. 64,65 Microscopic BPH was observed in all dogs after 6 y of age. 65 There are, however, important differences between human and canine prostatic anatomy and histology.…”

“…64,65 Microscopic BPH was observed in all dogs after 6 y of age. 65 There are, however, important differences between human and canine prostatic anatomy and histology. In human beings, there are clearly de®ned zones in the prostate.…”

“…Canine BPH is uniform and diffuse, occurring thoughout the entire gland and it primarily involves the glandular epithelial cells, with less stromal involvement. 45,61,65,67,68 Tunn and his colleagues 69 reported that the concentration of 5a-reductase, which converts testosterone to dihydrotestosterone, an active androgen, is higher in the prostatic epithelium than in the stroma in dogs. This is not the case in man which may explain why the hyperplasia is mainly epithelial in dogs and stromal in men.…”

Mensuração de hormônios andrógenos, estrógeno, fosfatase ácida prostática (PAP) e antígeno prostático específico (PSA) em cães adultos com próstata normal e hiperplásica

“…A HPB é um aumento espontâneo da próstata induzido por hormônios, freqüente em cães adultos e idosos, sendo considerada a alteração mais comum da próstata canina, visto que cerca de 100% dos cães adultos inteiros desenvolvem evidências histológicas de hiperplasia com o avançar da idade 2, 22,31,41 . Em relação aos fatores hormonais envolvidos na patogenia desta afecção, sabe-se que a testosterona, produzida nos testículos, é o principal andrógeno circulante do organismo, e dá origem a outros dois hormônios: a diidrotestosterona (DHT) e o 17β estradiol, sendo todos abarcados no estabelecimento do processo 28 .…”

Serum and urinary measurements of prostatic acid phosphatase (PAP) and prostatic specific antigen (PSA) in dogs

“…The prostate gland increases in size and weight, more frequently due to a hyperplasia or a neoplasia, as the animal gets older (Barsanti and Finco, 1989). A dog's prostate gland is the best natural model for the study of human prostate diseases, for similarities in the development of benign prostatic hyperplasia (BPH) and neoplasia (McEntee et al, 1987;Lowseth et al, 1990;Karr et al, 1995).…”