Effect of soy milk on histomorphometric changes of cerebellum in neonatal ovariectomized rats

Soy milk contains isoflavones that comprise the phytoestrogen families. The phytoestrogens are molecules derived from plants that have estrogen-like activity. They have structural similarities with mammalian estrogen. This study was done to investigate effect of soy milk on histomorphometric changes of cerebellum in neonatal ovariectomized rats. For this study, 30 female rats (one-day-old) were kept in standard laboratory conditions. Then 20 rats (one-week-old) were randomly selected and underwent surgical removal of the ovaries (OVX). Five rats were served for sham surgery, and the rest of 5 rats were considered as control study. The three OVX groups were treated on 14 days of age by soy milk (0.75 ml/kg), 1.5 ml/kg and 3 ml/kg respectively 2 times per day. At the end of two months, all rats were euthanized, blood samples were collected and the cerebellum was dissected and fixed in 10% formalin. Serial sections were obtained from prepared blocks and stained by H&E that were studied by light microscopy. Cerebellar histomorphological features included; measuring the thickness of the granular, molecular layers and Purkinje cells size in cerebellum gray matter, counting the cell number in these layers, estimating the thickness of the white matter, comparison of gray matter to the white matter in the cerebellum. According to this study, low estrogen level due to ovariectomized infant rats have reduced the thickness and cell number in most layers of the cerebellum. But, feeding high level of soy milk to ovariectomized infants induced high serum concentrations of 17-β estradiol that subsequently increased thickness and cells numbers of the cerebellum. Therefore the soy milk can be used as a source of synthetic hormone replacement.