PROTECTIVE ROLE OF VITAMIN B12 AGAINST METHYL-PARATHION TOXICITY IN OPHIOCEPHALUS (CHANNA) PUNCTATUS

Abstract

"PROTECTIVE ROLE OF VITAMIN B12 AGAINST METHYL-PARATHION TOXICITY IN OPHIOCEPHALUS (CHANNA) PUNCTATUS" Experimental studies were conducted to investigate the role of vitamin B12 against toxicity induced by methyl-parathion intoxication in a teleost fish, O.punctatus. To study the effect of methyl-parathion (O-0-dimethyl O-p-nitrophenylphosphorothionate) on behavioural, morphological, histopathological, haematological, histoenzymological and biochemical parameters in the liver, kidney and blood of fish, the healthy, living specimens of O.punctatus were collected measuring about 15 to 18 cm in length and 40-50 gm in weight. Bioassays have been conducted to gain preliminary information about the toxicity of MP on fish. The LC 50 values for 24, 48, 72 and 96h have been determined and were found to be 0.034 ml/1., 0.0056 ml/1., 0.0031 ml/1 and 0.0015 ml/1 of MP. For acute exposure, two sublethal concentrations of MP i.e., l/5th and l/10th fractions of LC5Q were selected. The results indicate that fishes exposed to high concentration (0.06 ml/1) of MP exhibit a significant degree of mortality after 24h exposure but there is a decline in mortality when the fishes are exposed to lower concentration (0.005 ml/1). Mortality rate decreases with the increase of exposure. The- data was collected at the four time intervals i.e., after 24, 48, 72 and 96h. Controls were also conducted simultaneously.

The behavioural response of fish towards toxicant was grossly dependent on concentration and period of exposure. After introducing the fish into test solution, the secretion of mucus from the body, hyperexcitability, increased aerial excursions and opercular movements were observed. Some fishes were characterized by the development of tremors and convulsions. Quantitative estimation of MP in tissue (liver, kidney) were done by HPLC. The absorption of MP concentration by the liver and kidney increased with the duration of the exposure time. After 96h exposure, the pesticide is completely absorbed by the tissues. Histopathologically, a number of degenerative changes were observed in the histology of the liver as nuclear pycnosis, nuclear mitosis, clumping of nuclei and hypertrophy of hepatocytes. The .liver damage was more severe after 96h exposure. The structure of the treated kidney show remarkable changes as loss of haemopoitic tissue, vacuolation, swelling of renal tubules, glomerular shrinkage and nuclear pycnosis in the renal tubules. After 96h exposure, the kidney damage was more severe due to MP intoxication. Irregular distribution of reticulin fibres and collagen fibres was also observed which show progression of tissue injury. Further, haematological investigation revealed a decrease in the haemoglobin percentage, haematocrit values and RBC counts, reflecting the anaemic state of fish, while

there was a slight elevation in the WBC counts. Other absolute values (MCV, MCH and MCHC) also altered in response to the changes in the above parameters. However, no significant alteration is found in all the acutely treated fish. Glucose, urea and cholesterol level increased significantly. Serum glutamic-oxalic transaminase, serum glutamic pyruvic transaminase and alkaline phosphatase increased while the acid phosphatase decreased in all the acutely treated fish. Biochemical observations include measurements of moisture . contents, total proteins, lipids and carbohydrates. Moisture contents and carbohydrates increased significantly. The tissue protein depleted maximally in the kidney while the tissue lipids depleted maximally in the liver after 96h intoxication. The enzymological alterations revealed significant inhibition in the alkaline and acid phosphatase activity and elevation in the lipase activity at all the time intervals both in the liver and kidney. The biochemical alterations in the enzymes were parallel to histochemical results. The effect of MP on liver, kidney and blood of fish is more severe after 96h exposure. Vitamin B, (dose of 0.25 ml) was injected in the intoxicated fish intramuscularly on each alternate day for two weeks. Administration of vitamin B12, shows loss of excessive secretion and deposition of the mucus on the body surface. Loss of lesions like hepatocytic necrosis, vacuolation and (iv) normal hepatocytes was observed after vitamin B 12 injection as evidenced by histopathological examination in the liver. No necrosis was observed in the kidney by vitamin B12 administration. A regular distribution of reticulin fibres was noticed in the liver while in kidney, intertubular accumulation of reticulin fibres was observed after vitamin B12 administration. No topographical differences in the distribution of collagen fibres was observed either in the liver or in the kidney. Anaemia, hyperglycemia and hypercholestremia was cured by vitamin B12 administration. MP induced glyconeogenesis in tissues is prevented by injecting vitamin B12- It is indicated that vitamin B12 provides protection to the fish against MP toxicity.