| The pyrethroid is a kind of pesticide and also used in aquaculture. They have good effects on preventing anchor, cootie and other carapace parasite of fish. But most of the pyrethroid are toxicity to fish and aquatic.This test selected fenvalerate to study, and selected one year grass carp which body weight was (109.27±15.26)g as the research object. This study related the drug-metabolizing enzymes (CYP3A), genetic damage, blood biochemical parameters and histopathological damage of fenvalerate on grass carp to evaluate the toxicity in aquaculture and accumulate scientific data for drug research.The 96 h semi-lethal concentration (96 h-LC50) of fenvalerat on grass carp of one year was 60.62μg/L. This study selected one-fiftieth, one-tenth and one-fifth of 96 h-LC50 as the test concentrations,1.2,6,12μg/L respectively, a blank control group, and enrofloxacin of 10 mg/L as a positive control. The CYP3A activtity in different tissues of grass carp and the effect of fenvalerat on the hepatic CYP3A activtity in the grass carp had been studied by the probe of erythromycin. The results showed that:the liver, gill, kidney, spleen, intestine and brain all had CYP3A. The CYP3A activtity in the liver was the most and higher than other organizations 1-3 times, and then was the gill, kidney, spleen, intestine and brain. The activity of the hepatic CYP3A could been significantly inhibited by fenvalerate, and enhanced with the exposed time. But the trend was weaken after 3 days and the inhibition of the activity was between 7.7% and 68.7% in this test. The test groups showed significant (P<0.05) and very significant (P<0.01) differences compared with the control except 1.2μg/L of fenvalerate exposured 1 day.This study selected 0,1.2,6,12μg/L dose of fenvalerate and cyclophosphamide of 650 ug/L as a positive control. The effect of genetic damage of fenvalerat on fish had been studied by micronulleus test on grass carp after exposed 1,3,6,9 days. The results indicated that when the fenvalerat was above 1.2μg/L, it could significantly increased the micronucleus rate, nuclear abnormities rate and the total nuclear anomalies rate. The highest micronucleus rate was 7.59×10-3, highter than the control 17.51 times, and the lowest was 2.07×10-3, highter than the control 4.05 times. The highest nuclear abnormities rate was 16.58×10-3, highter than the control 2.14 times, and the lowest was 3.87×10-3, lower than the control. The highest total nuclear anomalies rate was 21.4×10-3, highter than the control 3.06 times, and the lowest was 5.93×10-3, highter than the control 0.13 times. All the rates increased before the peak, and then declined slowly. And at some concentrations and some times, micronuclei rate had the correlations of dose-response and time-response.This study selected 0,1.2,6,12μg/L dose of fenvalerate and analyzed after exposed 1,2,3,6,9 days. The activity of aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP) and total protein (TP) in the serum of grass carp were measured by automatic biochemical analyzer. The results indicated that the activity of AST and ALT increased with the exposed time, but the ALT changes were later than the AST. The activity of ALP decreased, but only on the 9 days there were difference between the bank control(P<0.05). The total protein decreased as the exposed time within 6 days, but on the ninth day showed the trend of recovery. Fourth, the effect of fenvalerate on the histopathological damage.Through the observation of histopathology of gill, livre, kidney and muscle of grass carp, indicated that fenvalerate had some damage on grass carp. The gill became congestive when exposed 3 days. The gill mainly showed the epithelial cell of small piece of gil shedding, and unknown cell group, and turned more serious with the exposed time. The liver showed liver cells slightly expansion when exposed 3 days by 12μg/L of fenvalerate. The liver mainly showed hydropic degeneration, larger, rounder, and even necrosis with the exposed time increased. The live cell even showed mortitied when exposed 9 days by 12μg/L of fenvalerate.The kidney almost showed normal before exposed 6 days, after, mainly showed interstitial cells of kidney increasing and inflammatory cell infiltration and tubular cell of kidney hydropic degeneration. The skeletal muscle showed normal before 9 days except the dose of 12μg/L exposed 6 days. On the nine day, the silk texture of skeletal muscle arranged more and more disorder with the exposed dose.In summary, the dose of fenvalerate commonly used in aquaculture is between 1μg/L and 2μg/L. On this condition, fenvalerate that used once had no significant effect on CYP3A activity, blood biochemistry and kidney tissue damage. In the above concentration, fenvalerate could make the DNA of dividing cells damage, lead to deformity and cancer. When the fenvalerate was used again, it could inhibit the CYP3A. Fenvalerate more than 6μg/L could lead to gill, liver, kidney and skeletal muscle damage and metabolic disorder. This suggest that we must consider the type of combination drugs and the interval when use fenvalerate in aquaculture. In addition, it's a best choice that don't use fenvalerate or contained the composition in broodstock ponds and fry culture ponds.
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