Estrogen Receptors β Mediate the Protective Effect of Vitamin B12 on Seminiferous Tubular Epithelium of Cimetidine‐Treated Rats

Cimetidine is a commonly prescribed H2 receptor antagonist known for its antiandrogenic adverse effect. This effect occurs either by competitive blocking of the hydrotestosterone receptors in the pituitary gland, hypothalamus and/or the targeted tissues or by intervention with the conversion of testosterone into estrogen in the Sertoli cells. Additionally, prolonged use of the drug also causes nutritional disorders that affect the testis. One such example is inhibition of vitamin B12 absorption that eventually leads to vitamin B12 deficiency. Supplementation of vitamin B12 is postulated to protect against testicular damage caused by cimetidine. The aim of the present study was to investigate the microscopic and the ultrastructural changes induced by vitamin B12 on the germ cells and its effect on oestrogen receptors β (ERβ) in cimetidine‐treated rats. Materials and methods Twenty‐four adult male Sprague‐Dawley rats were used in the present study. They were divided into four groups (six animals each). Group I: received an intraperitoneal dose of saline. Group II: received a daily dose of 50 mg cimetidine/kg body weight intraperitoneally. Group III: received 3μg of Vitamin B 12‐hydroxocobalamin. Group IV: received a combination of the same doses of cimetidine and vitamin B12‐hydroxocobalamin. In all groups the injection was for 52 days, which is the period of rat spermatogenic cycle. At the end of the experiment, the animals were sacrificed, testicular biopsies were taken for light and electron microscopy and specimens were prepared for ERβ staining. The seminiferous tubules were morphometrically measured; thickness of the basement membrane was graded, and the intensity of the ERβ immunoreactivity was scored. Results Cimetidine‐treated group showed marked seminiferous tubular atrophy with epithelial disorganization, detachment of germ cells and reduction in the thickness of the germinal epithelium. The morphometrical analysis showed a significant increase in the standard tubular diameter with a significant decrease in the tubular luminal area and the epithelial areas. Furthermore, ultrastructure of this group showed irregular Sertoli cells with basal cytoplasmic vacuolation and a significantly thickened basement membrane. The immunoexpression of the ERβ was similar to control group (positive for all layers) with stained apoptotic cells. On the contrary, the animals of the Group III and IV showed near normal seminiferous tubules with spermatogenesis apart from small inter‐cellular vacuoles with some sloughed gem cells in the tubular lumen. The ultrastructure showed minimal cellular alteration and the Sertoli cells had less extensive changes compared to the cimetidine‐treated group. Immunoreactivity of the testicular sections of group III was very close to that of the control group with apparently no detectable histological findings. However, in Group IV the detached cells, spermatids, cytoplasm and the nuclei of primary spermatocytes were immunopositive. ERβ immunoreactivity in the few detected apoptotic cells was evident. Conclusion The present study proofs that ERβ affection mediates the role of vitamin B12 in decreasing the histological and ultrastructural damage of seminiferous tubules and maintaining the spermatogenesis after cimetidine administration. This may be an attempt to focus on the useful application of this vitamin for improvement of human or animal reproductive performance under normal or pathological conditions.