Effects of clonidine on myocardial beta-adrenergic receptor-adenyl cyclase-cAMP system after scalds in rats

AIM: To study the role of clonidine (Clo) on the myocardial beta-adrenergic receptor (beta-AR)-adenyl cyclase (AC)-cAMP system after the scalds in rats, METHODS: A 30 % skin-full-thickness scald was produced by immersing rats in 95 degrees C water for 9 s, Clo 0.1 - 3.0 mg . kg(-1) was injected ip to rats at 30 min before scalds, yohimbine (Yoh) 0.05 mg . kg(-1) or prazosin (Pre) 0.03 mg . kg(-1) to rats at 30 min before ip Clo, beta-AR density and affinity, AC activity, phosphoric diester hydrolases (PDH) activity, and cAMP content were determined with radioreceptor assay, indirect method, enzyme-radiochemical assay, and radioimmunoassay, respectivley. RESULTS: Clo inhibited the decrease of the myocardial beta-AR density, the attenuation of AC activity, and the reduction of cAMP content at 12 h after the scalds. Yoh partially reversed the effects of Clo on the three parameters. But Pra did not. CONCLUSION: Clo reversed the changes of the myocardial beta-AR-AC-cAMP system resulted from the scalds in rats.