Effect of Nicotine Injection and its Stoppage on Reproduction in Female Rats

Abstract

Background: There is a clear support for an association between smoking and decreased female fertility. The substantial harmful effects of cigarette smoking on fecundity and reproduction have become apparent but not generally appreciated. Aim of theWork: The present work aimed to study the effect of nicotine on some reproductive organs and the morphological abnormalities of the offspring of the nicotine-treated mothers. Material and Methods: The experimental female rats aged three-month old were divided into two main groups: Group A (nonpregnant rats) and group B (pregnant rats).Group A was subdivided into three subgroups eight rats each: (I) Saline-treated control subgroup that was injected with 0.9% saline subcutaneously daily for 3 weeks, (II) Nicotine-treated subgroup that was injected subcutaneously daily with nicotine in a dose of 0.4mg/100gm body weight which is equivalent to the amount of nicotine passing to the blood of the heavy smoker for 3 weeks and (III) a third subgroup, that was injected with nicotine in the same dose and for the same duration then left for 2 months without injection. Group B was subdivided into two subgroups eight rats each: (I) Control subgroup which was injected with 0.9% saline subcutaneously daily from the day 6 to the day 20 of pregnancy and (II) Nicotine-treated subgroup that was injected with nicotine in the same dose used in group (A) from the day 6 to the day 20 of pregnancy. The nonpregnant animals of subgroups A-I, II were sacrificed at the end of 3 weeks, whereas those of subgroup A-III were sacrificed 2 months later. The uterine and ovarian specimens were fixed in 10% formaline solution for histopathological examination. The pregnant rats of subgroups B-I, II were sacrificed on the 20th day of gestation, and the fetuses were extracted, examined by the naked eye and some of them were processed for Alizarin red staining for skeletal examination. The placenta was fixed in 10% formaline solution for histopathological and immunohistochemical examinations. Statistical analysis for evaluation of the effect of nicotine on pregnancy outcome and fetal growth was done. Results: As regards the histological changes in the ovary, nicotine caused retardation in the follicular growth, a decrease in healthy follicles and an increase in atretic and cystic follicles. Apoptotic granulosa cells were clearly observed. Fatty degenerative changes in corpora lutea were noticed. When nicotine injection was stopped, there was an improvement in the follicular growth with less degenerative changes in corpora lutea but they did not reach the control level. In the uterus, nicotine caused reduction in the endometrial and myometrial thickness and marked reduction in endometrial glands. When nicotine injection was stopped, although the endometrium and myometrium looked more or less similar to the control, the endometrial glands were reduced in some animals. Several placental degenerative changes were observed under nicotine treatment. The fetuses of nicotine-treated mothers showed several abnormalities including reduction in body size and weight, wrinkled skin, mis-shaped head, kyphosis, reduced neck region, micromelia, spina bifida and meningo-encephalocele. Also, the skeletal examination of Alizarin red-stained fetuses of nicotinetreated mothers revealed retarded ossification of axial and appendicular skeleton. The statistical analysis showed marked reduction in pregnancy outcome, fetal weight and length under nicotine treatment.