Vitamin D3 is a steroid hormone, like estrogens, and could regulate diverse female reproductive processes, including estrous cycles (EC) and uterine growth. Eighteen albino rats (138.33±8.37g BW) with regular EC, assigned into three groups (1-3, n=6), were used to investigate effects of vitamin D3 (vitD3) on EC length. Group 1 rats orally received 5 ml/kg BW distilled water (DW). Groups 2 and 3 orally received 0.025 mg/kg and 0.125 mg/kg of vitD3 dissolved in DW respectively for four weeks. Another 25 pre-pubertal rats (67.75±6.54g; 5 intact and 20 ovariectomized), assigned into five groups (A-E, n=5), were used to determine estrogenic activity of vitD3. Groups A (intact rats), B, C, D and E subcutaneously received 5 ml DW, 5 ml paraffin oil, 0.1 mg stilbesterol, 0.025 mg vitD3 and 0.125 mg vitD3 per kg BW, respectively for four days. Absolute uterine weights (AUW), relative uterine weights (RUW) and histomorphometric parameters of the uterine horns were recorded for rats of each group. The result showed that oral administration of 0.025 mg/kg BW vitD3 significantly (P<0.05) shortened proestrus and diestrus phases, but prolonged estrus phase of EC when compared with controls and 0.125 mg/kg BW group. However, total cycle length and metestrus phase were not affected. Similarly, 0.125 mg/kg BW vitD3 had no effect on EC or its phases. VitD3 and stilbesterol increased (P<0.05) AUW, RUW, endometrial thickness and uterine luminal folds when compared to the paraffin oil-treated and intact rats. Moreover, the endometrial thickness was higher (P<0.05) in paraffin-treated rats compared with the controls. It was therefore concluded that vitD3 altered EC of rats due to its estrogenic activity.

To Cite This Article: Mbegbu EC, Mbah CT, Obidike IR and Aka LO, 2021. Oral supplementation of vitamin D3 regulates estrous cycle due to its estrogenic effects in rats. Pak Vet J, 41(2): 294-298. http://dx.doi.org/10.29261/pakvetj/2020.104