Parry O, Okwuasaba F, Ejike C
Department of Pharmacology, University of Jos, Nigeria.
J Ethnopharmacol. 1988 Jan;22(1):33-44. doi: 10.1016/0378-8741(88)90228-0.
An aqueous extract of Portulaca oleracea leaves and stems produced a dose-dependent relaxation of guinea pig fundus, taenia coli and rabbit jejunum and a dose-dependent contraction of the rabbit aorta. On spontaneously-beating rabbit right atria and electrically-paced left atria, the extract produced a dose-dependent negative inotropic and chronotropic effects. On rat blood pressure, the extract produced dose-dependent pressor responses. Phentolamine reduced the relaxant effect of the extract on gut smooth muscle and abolished the contractile response on the aorta as well as the pressor response on blood pressure. Guanethidine and tetrodotoxin had no effect on extract-induced relaxant or contractile responses. On rat blood pressure atropine and cyproheptadine had no effect on extract-induced pressor response, whereas propranolol slightly reduced the pressor response. An increase in extracellular calcium reversed the inhibitory effect of the extract on the rabbit atria. The extract may, therefore, act in part on postsynaptic alpha-adrenoceptors and by interference with transmembrane calcium influx.
马齿苋叶和茎的水提取物对豚鼠胃底、结肠带和兔空肠产生剂量依赖性舒张作用，对兔主动脉产生剂量依赖性收缩作用。在自发性搏动的兔右心房和电刺激起搏的左心房上，该提取物产生剂量依赖性负性肌力和负性变时作用。在大鼠血压方面，该提取物产生剂量依赖性升压反应。酚妥拉明降低了提取物对肠道平滑肌的舒张作用，并消除了对主动脉的收缩反应以及对血压的升压反应。胍乙啶和河豚毒素对提取物诱导的舒张或收缩反应无影响。在大鼠血压上，阿托品和赛庚啶对提取物诱导的升压反应无影响，而普萘洛尔则略微降低了升压反应。细胞外钙的增加逆转了提取物对兔心房的抑制作用。因此，该提取物可能部分作用于突触后α-肾上腺素能受体，并通过干扰跨膜钙内流发挥作用。
