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Subject: Veterinary Pharmacology and Toxicology × Author: HEMANTH KUMAR, REGULAVALASA × End date: 2016 × Start date: 2010 ×
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    ThesisItemOpen Access
    IN VITRO STUDIES ON MODULATION OF CONTRACTILE AND RELAXANT RESPONSES IN SHEEP TRACHEAL SMOOTH MUSCLE BY CADMIUM
    (SRI VENKATESWARA VETERINARY UNIVERSITY TIRUPATI – 517 502. (A.P) INDIA, 2014-10) HEMANTH KUMAR, REGULAVALASA; Ravi Kumar, P (Major); Srinivasa Rao, G; Sailaja, N
    ABSTRACT: Cadmium is an environmental contaminant of increasing importance. Of various heavy metals, cadmium is known to have significant effect on the bronchial structures due to its portal of entry. In view of this, the present study is designed to know the modulatory effect of cadmium on the contractile or relaxant responses of various pharmacological agents like acetylcholine, salbutamol, sildenafil and sodium nitro- prusside in sheep tracheal smooth muscle in vitro. The control strips and the cadmium chloride treated strips were exposed to the contractile and relaxing agents like acetylcholine iodide, salbutamol, sildenafil and SNP in cumulative doses. At the end of each study the treated and the normal tissues were preserved for histopathological studies. Mean EC50 values for contractile response of acetylcholine obtained in the absence of cadmium chloride was 4.42 x 10-6M (1.9×10-8M to 1.9×10-5M) and in the presence of cadmium chloride it was increased to 6.43 x 10-5M (1.9×10-8M to 6.3×10-3M) with a significant right shift. Mean IC50 values for relaxant responses of salbutamol, sildenafil and sodium nitroprusside obtained in the normal sheep tracheal smooth muscle were 2.63 x 10-4M (1.9×10-8M to 6.3×10-3M), 3.66 x 10-4M (1.9×10-8M to 1.9×10-4M) , 8.64 x 10- 5M (1.9×10-8M to 1.9×10-4M) respectively. Cadmium chloride treatment resulted in a significant decrease in the mean IC50 values of salbutamol, sildenafil and sodium nitroprusside to 5.82 x 10-5M (1.9×10-8M to 1.9×10-4M), 2.17 x 10-5M (1.9×10-8M to 6.3×10-3M) and 4.48 x 10-6M (1.9×10-8M to 1.9×10-4M) respectively. Inhibition of acetylcholine induced contraction and promotion of relaxation mediated by salbutamol, sildenafil and sodium nitroprusside in isolated sheep tracheal smooth muscle by cadmium might be due to the blockade of Ca2+ channels. Mononuclear cell infiltration was seen in cut sections of trachea after cadmium treatment for 30 min. These cells are known to produce NO, which also might have aided the smooth muscle relaxation. The decreased [Ca2+]i and mononuclear cell mediated NO production together might be responsible for the relaxant effect of cadmium on sheep tracheal smooth muscle