Prolactin induced cyto-architectural changes in the corpuscles of Stannius of stinging catfish, Heteropneustes fossilis acclimated to different calcium media

Adult fish Heteropneustes fossilis were divided into 4 groups –(i) Group A: kept in artificial freshwater and daily injected intraperitoneally with vehicle; (ii) Group B: kept in artificial freshwater and were daily injected intraperitoneally with 0.1 mg/100 g body wt of oProlactin; (iii) Group C: maintained in calcium-deficient freshwater and daily injected intraperitoneally with vehicle; (iv) Group D: kept in calcium-deficient freshwater and daily injected intraperitoneally with 0.1 mg/100 g body wt of oProlactin. Blood samples were taken 2 h after the last injection on 1, 3, 5, 10 and 15 days of the treatment. Plasma calcium levels were analyzed. The corpuscles of Stannius (CS) were fixed for histological studies. Artificial freshwater: The plasma calcium levels of vehicle-injected specimens (group A) remained unaltered throughout the experiment. Following prolactin treatment (group B) the plasma calcium levels progressively increased from day 3 to day 5. The values became normocalcemic at day 10 and day 15. After day 5 following prolactin administration (group B), the nuclear volume of AF-positive cells increased and the cells were seen degranulated. After day 10, there was an increased dilatation of sinusoids and the nuclear volume of AF-positive cells showed further increase. On day 15, these changes were exaggerated. The AFnegative cells of the corpuscles of Stannius of prolactin-treated fish (group B) showed no change in their histological structure and nuclear volume. Calcium-deficient freshwater: The plasma calcium level decreased in vehicle-injected fish (group C) from day 1 to day 3 (as compared to level of the fish kept in artificial freshwater). Thereafter, the level increased from day 5 resulting in hypercalcemia at day 10 and day 15. In prolactin treated fish (group D) the plasma calcium level indicated progressive increase from day 5 to day 15. In the vehicle-injected fish (group C) the AF-positive cells of corpuscles of Stannius showed accumulati