Metalaxyl-induced bradycardia in rats: mediated by alpha-adrenoreceptors.
The effect of the fungicide metalaxyl [methyl N-(2-methoxyacetyl)-N-(2,6-xylyl)-DL-alaniate] on cardiac activity was investigated in albino rats anesthetized with phentobarbitone. Metalaxyl caused dose-dependent bradycardia, and at higher doses (250 and 300 mg/kg body weight) the sustained bradycardia led to cardiac arrest. The acetylcholinesterase activities in brain and heart were not affected in metalaxyl-treated rats. However, the bradycardia induced by the fungicide was blocked by pretreatment of rats with the alpha-adrenoreceptor antagonist phentolamine (20 mg/kg, ip). The data suggest that the bradycardia-inducing effect of metalaxyl was not mediated by the cholinergic system but through alpha-adrenoreceptors.
Naidu
K A
KA
Department of Nutrition and Food Safety, Central Food Technological Research Institute, Mysore, India.
Radhakrishnamurty
R
R
D000409:Alanine / Q000031:analogs & derivatives* / Q000633:toxicity; D000818:Animals; D001919:Bradycardia / Q000139:chemically induced*; D005260:Female; D005659:Fungicides, Industrial / Q000633:toxicity*; D006323:Heart Arrest / Q000139:chemically induced; D006339:Heart Rate / Q000187:drug effects; D007274:Injections, Intraperitoneal; D008297:Male; D010646:Phentolamine / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects*
D005659:Fungicides, Industrial; D011942:Receptors, Adrenergic, alpha; C028175:metalaxyl; D000409:Alanine; D010646:Phentolamine