Irradiation of the testes of four to 13-year-old male beagles with benign prostatic hyperplasia (BPH) was undertaken to attempt to evaluate the possibility that the testes secrete a non-androgenic accessory sex gland-stimulating substance that may have a critical role in the development of BPH. Available evidence indicates 1) that development of prostatic hyperplasia in dog and man is dependent on testicular secretions and 2) that testes irradiation is unlikely to alter testosterone secretion appreciably but does produce profound effects on the seminiferous tubules. Thirteen non-irradiated and shoulder irradiated control and 16 beagles subjected to 1500 to 2200 rads single dose testis irradiation had pre-irradiation, interval post-irradiation and terminal caliper measurements of prostatic length, width and depth, prostatic and testicular biopsies, and determination of serum testosterone and estradiol levels. Four beagles survived in a group observed for 109 weeks post testis irradiation, 12 in a group observed for 51 and 10 in a group observed for 59 weeks. The wet weight of the prostate was determined at sacrifice. Ratios of the final/initial length and width and final actual/initial calculated weight of the prostate were significantly decreased in testis-irradiated as compared to control beagles. Histologic evaluation also demonstrated a significant difference in degree of prostatic stimulation in control and testis-irradiated groups. The serum testosterone and estradiol levels were not significantly different in the testis-irradiated and control beagles. These observations indicate that irradiation of the testes of beagles with BPH alters the size, weight and histology to suggest decreased stimulation of the prostate without producing an identifiable change in the serum levels of the steroid hormones studied. The data support the hypothesis that the testis of the aging beagle secretes a non-androgenic and probably non-steroidal prostatic stimulating substance which is affected by irradiation of the testis.
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