STRUCTURAL-CHANGES OF SMALL RESISTANCE ARTERIES IN SPONTANEOUSLY HYPERTENSIVE RATS AFTER TREATMENT WITH VARIOUS DOSES OF LACIDIPINE

Objective To evaluate the modifications of the morphology of mesenteri c small resistance vessels in spontaneously hypertensive rats (SHR) in duced by lacidipine treatment, Methods Lacidipine was administered at three different dosages, 20, 10, and 0.3 mg/kg per day, Fifty rats wer e studied, Nine SHR and 11 Wistar-Kyoto (WKY) rats were not treated, E ach lacidipine dose was administered to 10 SHR, The drug and the place bo were administered by gavage from age 4 to age 12 weeks, The blood p ressure was measured noninvasively every week, The animals were killed when they were aged 13 weeks, and the relative left ventricular mass (left ventricular weight plus septum weight/body weight) was calculate d, Small mesenteric resistance vessels were dissected and mounted on a micromyograph (Mulvany's technique), and morphological parameters of the vessels were studied (media thickness and media:lumen ratio), Resu lts The systolic blood pressure of SHR administered 20 and 10 mg/kg la cidipine per day was reduced significantly during the treatment period , whereas that of rats treated with 0.3 mg/kg lacidipine per day did n ot change, A significant reduction in media:lumen ratio was observed f or all three groups of treated rats, including those to which 0.3 mg/k g lacidipine per day had been administered, and no reduction in systol ic blood pressure could be detected, The relative left ventricular mas s was reduced significantly only in rats to which 20 and 10 mg/kg laci dipine per day had been administered, Conclusion A significant reducti on in magnitude of vascular structural alterations was observed even i n SHR treated with a low, nonhypotensive dose of lacidipine.