Effect of Dimethoate on Prolactin Cells of Freshwater Catfish Heteropneustes fossilis after Short-term and Long-term Exposure

The effects of dimethoate on pituitary prolactin cells of Heteropneustes fossilis was investigated in this study. The fish Heteropneustes fossilis were subjected to sub-lethal concentration of dimethoate - 2.24 mg/l i.e. 75% of 96 h LC50 for short-term (24, 48, 72 and 96 h), and 1.00 mg/l i.e. 25% of 96 h LC50 for long-term (6, 12, 24 and 36 d) exposure. Pituitary was removed from anaesthetised fish and fixed for histological examinations. H. fossilis exposed for short-term (96 h) at sub-lethal dimethoate concentration, exhibited marked changes in structure and staining properties of prolactin cells. PRL cells did not show much histological alterations after 24 h, however, after 96 h exposure exhibited severe vacuolization and nuclear pycnosis, indentation and deformity of nuclear boundaries. In long-term dimethoate exposure the PRL cells of Heteropneustes fossilis, exhibited low staining response invisible vacuolization and distinct nuclear boundaries after 6 day. However, severe vacuolization, pycnosis and the nuclear diameter reduction in PRL cells were noticed after 24 d and 36 d exposures. The study concluded that dimethoate affects calcium regulating prolactin (PRL) cells and disturb the calcium homeostasis of fish which is important for fish health and their survival.