P13: Variation in weight and histological appearance with maturity of the prostate in control beagle dogs used in preclinical studies from two suppliers

Sexual immaturity of dogs can hamper accurate identification of compound-related changes. Knowledge of anatomical variations and development will allow accurate interpretation of observed changes. The aim of this work was to investigate the variation with age of the microscopic appearance of the testis and prostate in control beagle dogs from two sources. Data were extracted from the records of toxicity studies undertaken with control male Beagle dogs obtained from two suppliers, Marshall Farms USA and Harlan France, at MDS between 2001 and 2007. This represented 125 male Beagle dogs, from 23 to 108 weeks of age. HE stained sections of the prostate and testes were examined for all dogs. The degree of acinar development, the absence or presence of secretion in the prostate, and testicular maturity were recorded. We observed that the prostatic secretion increased with the age of dogs, in parallel to the prostatic development and testicular maturity. Moreover a clear difference was observed between suppliers: Acinar development was complete by 31 weeks of age in Harlan dogs against 43 weeks of age in Marshall dogs. This correlated with the testicular maturity. These data were consistent with the literature. Spontaneous variations in the morphology of the prostate may influence the assessment of toxicological data. It is important to be aware of sexual maturity, and to know the normal age-related variations of the prostate's histological appearance in the species used.