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 i.p. to rats at 30 min before scalds, yohimbine (Yoh) 0.05 mg.kg-1 or prazosin (Pra) 0.03 mg.kg-1 to rats at 30 min before i.p. Clo. beta-AR density and affinity, AC activity, phosphoric diester hydrolases (PDH) activity, and cAMP content were determined with radioreceptor assay, indirect method, enzymeradiochemical assay, and radioimmunoassay, respectively.

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.