Histo-cytological responses of the prolactin cells of the catfish Heteropneustes fossilis to cadmium exposure

Cadmium is an important metal for modern industrial processes and being biologically non-essential poses health hazards to the organisms. In this study we aimed to evaluate the effect of cadmium exposure on the histo-cytology of prolactin cells in the fish, Heteropneustes fossilis. Heteropneustes fossilis were subjected to 288 mg/L (0.8 of 96 h LC50) and 72 mg/L (0.2 of 96 h LC50) of cadmium chloride for short-term and long-term, respectively. After sacrificing the fish, the blood was collected on 24, 48, 72 and 96 h in short-term and after 7, 14, 21, and 28 days in long-term experiment and analyzed for plasma calcium levels. Also, pituitary glands were fixed on these intervals.The plasma calcium levels of short-term cadmium exposed fish remain unchanged after 24 h. The levels exhibit a progressive decrease from 48 h onwards. The fish exposed to cadmium for 7 days exhibit a decrease in the plasma calcium level. Thereafter, the levels progressively decrease till the end of the experiment (28 days).The prolactin cells of the control fish exhibit structural resemblance to the description given for the prolactin cells of normal H. fossilis. No change in the histological structure and nuclear volume of prolactin cells of cadmium exposed fish has been noticed throughout the experiment. In cadmium treated fish the prolactin cells remain unchanged till 14 days. On day 21, the nuclear volume of these cells exhibits an increase and the cells are seen degranulating. These changes increase profoundly on day 28. In addition vacuolization and cytolysis are also encountered on day 28 following cadmium treatment. It is concluded that cadmium affects the prolactin cells of the fish H. fossilis thus disturbing the ionic balance.