EFFECT OF ANTIHYPERTENSIVE TREATMENT WITH FOSINOPRIL ON MECHANICAL PROPERTIES OF SMALL MESENTERIC ARTERIES OF SPONTANEOUSLY HYPERTENSIVE RATS: PP.11.433

Abstract

A pronounced fibrosis, as documented by an increased collagen:elastin ratio may be observed in the tunica media of mesenteric small resistance arteries of spontaneously hypertensive rats (SHR), compared with Wistar-Kyoto controls (Sharifi EM et al, J Hypertens 1998; 16:457–466). However, the consequences of such fibrotic changes in the microvasculature in terms of elastic properties are controversial, and either no change or a paradoxical increase in distensibility/decreased elastic modulus was observed in SHR (Mulvany MJ, Hypertension 1992 20: 7–9; Laurant P et al, J Vasc Res 1997, 34: 117–125). The aim of this study was to evaluate the effects of the ACE inhibitor fosinopril given either at hypotensive, high dose (FOS hd) or at a non-hypotensive, low dose (FOS ld), on mechanical properties (relationship between incremental elastic modulus/wall stress) of mesenteric resistance arteries in SHR, compared with WKY controls. Fosinopril was administered in the drinking water from the 6th to the 12th week of age. Rats were sacrificed at 12 weeks of age and heart weight/body weight ratio was measured. Mesenteric arterioles were dissected and mounted on a micromyograph (Mulvany's technique), and the media to lumen ratio (M/L) was measured. Results are summarized in the Table (** = p < 0.01 vs. untreated SHR; #p < 0.001 vs. untreated WKY).During the 6 weeks of treatment, systolic blood pressure in SHR treated with high dose fosinopril was significantly lower in comparison with untreated SHR, while no difference was observed with low dose fosinopril. On the contrary, in SHR treated with both high dose and low dose fosinopril, a statistically significant reduction of M/L was observed. However, no difference in the relation between incremental elastic modulus and wall stress of mesenteric resistance arteries between untreated SHR and WKY, or between treated and untreated SHR was observed. In conclusion, our data suggest that changes in the structure of mesenteric small resistance arteries in SHR are not associated with parallel changes in the mechanical properties/vascular distensibility.