Effects of cadmium on plasma cortisol and prolactin levels in the rainbow trout [oncorhynchus mykiss]

ABSTRACT

Cadmium occurs as a contaminant in freshwater systems, primarily are a result of lead mining, smelting and electroplating. In freshwater fish, prolactin and cortisol are thought to be in volved in the maintenance of ionic and osmotic balance and since this regulation is apparently disrupted by cadmium, related changes in prolactin and cortisol might occur. In view of this, it was decided to investigate the effect of cadmium on plasma cortisol and prolactin levels in the rainbow trout. The objectives of this research were to determine the LC50 values during 120 h period after acute exposure to poison of cadmium chloride. The LC50 values for 24, 48, 72, 96 hours were, found to be 7.76, 1.95, 0.5, 0.45 mg/lit respectively. Exposure of rainbow trout to 10, 1, 0.5 mg/lit cadmium during 24h did not have any change in plasma prolactin levels [p>0.05]. Exposure of fish to 0.1 mg/lit cadmium 5, 24, 48, 96 hours in tank water produced time dependent changes [p=0] in plasma prolactin levels. Exposure of trout to 0.05 mg/lit cadmium did not change plasma prolactin levels [p>0.05]. Exposure of trout to 0.05 mg/lit cadmium for 24 and 27 h. didnot have any change in plasma cortisol levels [p=0.08]. Exposure of trout to 0.1 mg/lit of cadmium in the tankwater in 5, 24, 28, 26 h. Producedtime dependent changes in plasma cortisol levels which may reflect the alarm resistance and exhaustion stages in the response of the fish to the cadmium