Abstract

Background
Previous studies have shown that nicotine enhances oxidative DNA damage and leads to increased lipid peroxidation, which affects embryo development. The present study investigated the effect of daily supplementation of gamma-tocotrienol on oocytes of nicotine-treated mice.
Material and Method
Immature female mice (18-25 g) were divided into three groups. For 30 days, group A (control group) received saline (0.2 ml/day s.c.), group B nicotine (5 mg/kg/day s.c. in saline), and group C nicotine with gamma-tocotrienol (60 mg/kg/day p.o.). The animals were superovulated following these schedules.
Results
Scanning electron microscopy (SEM) showed that the nicotine-treated oocytes appeared nonspherical with rough surface and the zona pellucida (zp) was torn and became irregular. Supplementation with gamma-tocotrienol in the nicotine-treated mice retained the spherical shape of the oocytes with intact zp; however, the surfaces of the oocytes remained irregular and rough. Transmission electron microscopy (TEM) following chronic nicotine treatment showed loosening of the boundary and tearing of the zp. The perivitelline space was also widened. The cytoplasm of the oocytes retained abundant rough endoplasmic reticulum (rER) with numerous vesicles. Mitochondria were highly dense, with no cristae. The administration of gamma-tocotrienol partially reduced the detrimental effects of nicotine by retaining the smooth boundary of the zp with the tight perivitelline space. There was less rER with no visible vesicle and a lower amount of dense mitochondrial matrix.
Conclusions
This study documented that chronic nicotine treatment adversely affects the ultrastructure of oocytes, while gamma-tocotrienol treatment at least minimizes the nicotine-induced damage to oocytes.

Keywords: Vitamin E - pharmacology, Oxidative Stress - drug effects, Oocytes - ultrastructure, Nicotine - toxicity, Microscopy, Electron, Scanning, Microscopy, Electron, Transmission, Mice, Inbred Strains, Malondialdehyde - blood, Lipid Peroxidation - drug effects, Endoplasmic Reticulum, Rough - ultrastructure, Chromans - pharmacology, Zona Pellucida - ultrastructure