EFFECTS OF XINCHUANLING (XC-1) AND ITS DERIVATIVE XC-2 ON ADRENOCEPTORS AND ARTERIAL MUSCLE

Xinchuanling (XC-1) is a compound synthesized by the Henan Institute of pharmaceutical Industrial Research. (XC-2) is a derivative of XC-1. In this paper, the effects of XC-1 and XC-2 on adrenoceptors and arterial muscle were studied.XC-1 and XC-2 exhibited moderate affinity for α₁-(Ki, 2.94±0.45 and 2.71± 0.74μM) and α₂-adrenoceptor (Ki, 4.0±2.1 and 4.8+1.2μM) of rat brain cortex and a low affinity for β-adrenoceptor (Ki, 22.3 and 24.1 μM) of duck erythrocyte membrane.The intrinsic activity of XC-1 and XC-2 for α₁-adrenoceptor were determined on isolated rat anococcygeus muscle and rabbit aorta using NE as an α-adrenergic agonist. After addition of the two drugs in the medium at concentration of 10^-5, 4×10^-5 and 8×10^-5mol/L, the cumulative dose-response curve of NE was shifted to the right but the maximum response was lower than that of the control. XC-1 and XC-2 were shown to have no significant effect on presynaptic α₂-adrenoceptor in experiments using field stimulation-induced contraction of vas deferens as criterion.The adenylate cyclase (AC) of the duck erythrocyte membrane and rat lung was not activated by the two drugs. However, the effects of activation of AC by isoprenaline were inhibited by XC-1 and XC-2.The effects of the two drugs on the adrenoceptors was found to be similar.The contractions of isolated rabbit aorta induced by K²⁺ or Ca²⁺ were markedly inhibited by XC-1 and XC-2. The cumulative dose-response curves of K²⁺ and Ca²⁺ were shifted to the right by these two drugs.In addition to the effects of blocking α₁-and β-adrenoceptors and antagonism of Ca²⁺, XC-1 also diminished the 5-HT induced contractile force of rabbit aorta and exhibited a direct relaxation on this preparation. According to the multiplicity of the mode of action of these two drugs, it would appear that they may be used in the treatment of some cardiovascular diseases with little side effect.