Greeberg S
J Pharmacol Exp Ther. 1980 Nov;215(2):279-86.
Minoxidil and hydralazine are related in chemical structure. Minoxidil is effective for the treatment of hypertensive emergencies. This drug lowers total peripheral resistance and has a direct vasodilator action, in vivo, its mechanism of action is unknown. The present study evaluated the effects of chronic oral administration of minoxidil and hydralazine on the contractile and passive physical properties of protal veins and small (0.4-0.6 mm outside diameter) mesenteric arteries from spontaneously hypertensive Okamoto-Aoki rats. Minoxidil or hydralazine was added to the drinking water of spontaneously hypertensive rats for 14 days. Blood pressure and heart rate were measured every second day. The contractile responses of mesenteric arteries and portal veins were measured in vitro. Minoxidil (0.3-10 mg/kg/day) produced a dose-related reduction in blood pressure. The in vitro sensitivity (ED50) and maximal contractile tension development of mesenteric arteries to norepinephrine, angiotensin, calcium chloride, potassium chloride and prostaglandins D2, E2, F2 alpha, B2 and A2 were not affected by chronic treatment of spontaneously hypertensive rats with minoxidil. In portal veins, minoxidil did not affect the ED50 or maximal tension development to any agonist. Minoxidil decreased the passive stiffness of portal veins. Hydralazine (1-100 mg/kg/day) decreased arterial pressure and depressed the maximal contractile tension and passive stiffness of both mesenteric arteries and portal veins. The data suggest that the antihypertensive action of minoxidil and hydralazine may not be related to a direct depressant action of the drugs on vascular smooth muscle function. It is possible that hydralazine and minoxidil, although somewhat similar in structure, may lower blood pressure by two different mechanisms. Alternatively, the action of these two drugs may be similar but reside in sites other than the vascular smooth muscles studied.
米诺地尔和肼屈嗪在化学结构上相关。米诺地尔对治疗高血压急症有效。该药可降低总外周阻力并具有直接血管舒张作用，在体内，其作用机制尚不清楚。本研究评估了长期口服米诺地尔和肼屈嗪对自发性高血压冈本 - 青木大鼠门静脉和小（外径0.4 - 0.6毫米）肠系膜动脉的收缩和被动物理特性的影响。将米诺地尔或肼屈嗪添加到自发性高血压大鼠的饮用水中，持续14天。每隔一天测量血压和心率。体外测量肠系膜动脉和门静脉的收缩反应。米诺地尔（0.3 - 10毫克/千克/天）使血压呈剂量相关下降。自发性高血压大鼠长期用米诺地尔治疗后，肠系膜动脉对去甲肾上腺素、血管紧张素、氯化钙、氯化钾以及前列腺素D2、E2、F2α、B2和A2的体外敏感性（ED50）和最大收缩张力发展不受影响。在门静脉中，米诺地尔对任何激动剂的ED50或最大张力发展均无影响。米诺地尔降低了门静脉的被动僵硬度。肼屈嗪（1 - 100毫克/千克/天）降低动脉压，并降低肠系膜动脉和门静脉的最大收缩张力和被动僵硬度。数据表明，米诺地尔和肼屈嗪的降压作用可能与药物对血管平滑肌功能的直接抑制作用无关。有可能肼屈嗪和米诺地尔虽然结构有些相似，但可能通过两种不同机制降低血压。或者，这两种药物的作用可能相似，但存在于所研究的血管平滑肌以外的部位。
