西施花之正丁醇抽取物引起離體家兔主動脈血管收縮機轉之研究

A Study of Action Mechanism of Vasocontraction Induced by Butanol Extract of Rododendron Ellipticum on the Isolated Rabbit Aorta

西施花(Rhododendron ellipticum Maximowicz)為杜鵑屬之植物，文獻記載有降血壓、鎮痛等功效。本研究將西施花的葉利用不同的有機溶媒給予分離，就其中藥效較強的正丁醇層抽出物之水溶部分（簡稱R.E.），進一步探討其對於離體家兔動脈血管之作用機轉。獲得如下之結果：一、於離體實驗中，R.E可以使離體兔主動脈血管收縮，其作用隨著劑量的增加而增強；其收縮強度，在累積劑量下較一次向劑量為弱。血管內皮的去除，R.E.對於血管收縮作用減弱。二、R.E.對於離體兔主動脈產生之血管收縮作用，可以因利用組織胺釋放抑制劑(cromolyn sodium)、H1阻斷劑(diphenhydramine)和5-HT阻斷劑(cyproheptadine和ketanserin)預先處理而減低；H1阻斷劑對於R.E所致血管收縮之抑制作用，可因併用H2阻斷劑(cimetidine和ranitidine)所加強；又鈣離子阻斷劑(verapamil)亦會抑制R.E.之收縮作用；若以calcium-free溶液取代Krebs氏液，同樣可以使R.E之收縮作用減低。以土結果顯示，R.E對於離體家兔動脈血管之作用，主要係與組織胺受體之興奮，可能有部分經由5-HT受體的作用，而且其作用需要鈣離子及內皮細胞之同時存在。

The effects of butanol extract of Rhododendron ellipticum (R.E.) on the isolated rabbbit aorta were studied. The following results were obtained. (1) The isolated rabbit aorta was contracted by R.E. dose-dependently. The effect was decreased while the endothelium was removed. R.E. produced less contraction in a accumulated dosage administration than in a single one. (2)R.E. -induced contraction was attenuated by pretreated with histamine release inhibitor (cromolyn sodium), H1 antagonists (diphenhydramine) and 5-HT antagonists (cyprohyptadine and ketanserin). The inhibition of H1 antagonists on the R.E. induced vasocontraction was potentiated by combination with H2 antagonists (cimetidine and ranitidine) which were no effect alone. The vasocontraction induced by R.E. was inhibited by calcium blocking agent, verapamil. In addition, the effect was also decreased in calcium-free solution. From the above results, we suggested that R.E.-induced vasocontraction was primarily via the stimulation of histaminergic receptors and partly via the activation of serotonergic receptors. The coexistence of calcium and endothelium was necessary for this effect.