Effect of methanol extract of soy on testicular morphometry and plasma testosterone levels

Abstract

Background: Soy is endowed with certain estrogen-like substances including isoflavones such as genistein and daidzein; these phytoestrogens are capable of binding to estrogen receptors a and ß, and could therefore trigger estrogen-dependent physiological responses. Thus, we studied the effect of methanol extract of soy on testicular morphometry and plasma testosterone levels in a model of Wistar rats. Methods: Two groups of rats (12-14 weeks old) weighing 90-98 g were assigned either normal saline or 1.50 mg/kg/d of methanol extract of soy by gavage for 8 weeks. The testes of each rat were then harvested and processed for stereological and morphometric analysis using the haematoxylin and eosin method. Plasma testosterone concentrations were also estimated using the testosterone immunoassay test kit. Results: Tubular diameter, cross-sectional area of seminiferous tubules, mean percentage volume of seminiferous epithelium and plasma testosterone level decreased significantly (P<0.05) from 90.75 µm, 6.47x103 µm2, 55.63 %, and 0.3 ng/ml respectively in the control to 44.50 µm, 1.45x103 µm2, 31.09 % and 0.12 ng/ml in the soy-treated group. Conversely, the number of profiles of seminiferous tubules per unit area of the testis, mean percentage volume of testicular stroma and mean percentage volume of tubular lumen increased (P<0.05) from 11.25x10-8 µm–2, 22.49 % and 21.88 % respectively, in the control to 28.75x10-8 µm –2, 39.51 %, and 29.40 % in the treated group. Conclusion: These findings in rats are suggestive of the potential deleterious effect of soy phytoestrogens on testicular cytoarchitecture and plasma testosterone levels, with negative implications for male fertility.