Reduced renal mass hypertension, but not high salt diet, alters skeletal muscle arteriolar distensibility and myogenic responses

The effects of high salt diet and reduced renal mass hypertension (RRM-HT) on skeletal muscle arteriolar distensibility and myogenic responses were in vestigated in male Sprague-Dawley rats. Rats were enclosed in an airtight b ox with the in situ cremaster muscle exteriorized and viewed via television microscopy. Normotensive rats were fed low salt (0.4% NaCl) or high salt ( 4.0% NaCl) diet and RRM-HT rats were fed high salt diet for 4-6 weeks. With the cremaster muscle superfused with either physiological salt solution (f or myogenic responses) or Ca2+-free physiological salt solution (for arteri olar distensibility), box pressure (and therefore, intravascular pressure) was increased in 5 mm Hg increments to a maximum of +30 mm Hg. The myogenic responses of arterioles were not altered by high salt diet, but were enhan ced with RRM-HT. Arteriolar distensibility was not affected by high salt di et, but was reduced in RRM-HT rats compared to either normotensive rat grou p. These data suggest that high salt diet does not significantly alter eith er myogenic responses or the distensibility of rat cremasteric arterioles. However, RRM-HT enhances myogenic responses of these vessels while reducing arteriolar distensibility. The impact of these effects must be taken into account when interpreting data describing alterations in skeletal muscle mi crovessel reactivity for animals on high salt diet or with RRM hypertension . (C) 2000 Academic Press.