Effects of an anabolic steroid (Durateston) on testicular angiogenesis in peripubertal stallions

The aim of this study was to determine the effect of the anabolic steroid testosterone on the testicular vascularization, angiogenesis and expression of angiogenic factors, and their receptors in testes of peripubertal stallions. Seven peripubertal stallions were treated with Durateston and castrated either 4 (treatment group 1 [TG1]) or 12 weeks (TG2) after the last injection. The castration of seven untreated control stallions (control group [CG]) took place within the same time. In the testicular specimens, volume density (VD), numerical density (ND), and area of vessels were determined morphometrically. Immunohistochemically, the expression of vascular endothelial growth factor (VEGF) and its receptor VEGF-R2; angiopoietin 2 (Ang2) and its receptor Tie2 as well as of transforming growth factor α (TGF-α) was investigated. Morphometrically, the VD of TG1 (P = 0.000) and TG2 (P = 0.001) vessels and the ND of arterioles and venules and capillaries were higher (TG1, TG2: P < 0.05), and the area of capillary cross sections was smaller (TG1, TG2: P < 0.05) than that in the CG. Compared to TG2 horses, TG1 animals showed a higher (P < 0.05) VD and ND of vascular structures and a smaller (P < 0.05) area of capillary cross sections. In numerous vascular structures, especially of TG1, the TGF-α and, to a less extent, the Ang2 and VEGF-R2 expression was significantly higher (P < 0.05) than that in the CG. Sertoli cells in TG2 were characterized by a significantly higher expression (P < 0.05) of VEGF-R2 than in the CG. In summary, the most and smallest vessels could be detected in the testes of TG1. Most likely this is explainable by the highest expression of some angiogenic factors (TGF-α, Ang2) and receptors (VEGF-R2) investigated. This expression behavior may be stimulated by testosterone. As a significant decrease of morphometric parameters could be detected in TG2 compared to TG1, the stimulatory effect of testosterone seems to be temporary.