Effects of nicotine on growth, survival rate, skeletal system and visceral organs in zebra fish (Danio rerio): A histopathological and immunohistochemical study

Although Nicotine is one of the most potent toxins in the world, in order to prevent smoking, it has been used as replacement therapy, and has been given to patients through gums, dermal patches, lozenges and inhalers. Zebrafish are excellent model organisms and are widely used in biomedical and genetic related human diseases. The aim of this thesis was to evaluate the effects of nicotine on the growth performance, survival rate, skeletal system, visceral organs of zebra fish larvae and adults. Histology and immunohistochemical staining methods were applied in order to detect adverse effecst of nicotine on the cellular and molecular level. As in humans, marker of cell proliferation Kiel 67 (mki-67) and tumor suppressor protein (TP53) are highly conserved in zebra fish. Therefore, mki-67and TP53 were chosen as antibodies. Four hundred and eighty newly hatched larvae were divided into four experimental groups namely: thhe groups contain nicotine as Control (C, 0 mg·L–1), N1 (N1, 5 mg·L–1), N2 (N2, 10 mg·L–1) and N3 (N3, 20 mg·L–1). The results showed that nicotine had an detrimental effect on the growth and survival rate of zebra fish. The experimental groups exposed to Nicotine showed lower final weight and length compared to the control and were statistically significant. 20 mg·L–1 Nicotine dosage used in the present study had the most negative effect on growth and survival rate. Morphological observation indicated major bleeding in visceral organs when compared to the control groups. Increased nicotine dosages were associated with increased risk of major bleeding in muscle, liver, gonads, swim bladder, kidney and intestine. Moreover, histopathological effects of nicotine on the muscle, liver, intestine, kidney and gonads were recorded. Mononuclear cells, vacuolization and infarction of cell were clearly recorded in all visceral organs. Most detrimental effects of nicotine were recorded in the highest dosage of 20 mg·L–1 nicotine exposed groups. At the molecular level; liver, kidney, muscle, gonads and intestine cells were mki-67 positive. Liver and kidney stained P53 positive at all dosages, whereas gonads and intestine stained positive only at the highest dosage. No staining was observed in the muscles. It is shown that nicotine can adversely affect the skeletal system, body color, growth and survival rate. On the cellular and molecular level dosage related detrimental effecst of nicotine were clearly detected in all visceral organs. Therefore, cautions should be taken when used as nicotine replacement therapy.