Jc. Frisbee et al., Contribution of extrinsic factors and intrinsic vascular alterations to reduced arteriolar reactivity with high-salt diet and hypertension, MICROCIRCUL, 7(4), 2000, pp. 281-289
Objective: To determine whether relaxation of skeletal muscle arterioles of
rats on high-salt diet or with reduced renal mass hypertension (RRM-HT) re
presents intrinsic alterations to microvessels alone, or whether extravascu
lar influences also contribute to reduced dilator responses.
Methods: Normotensive (NT) Sprague-Dawley rats were fed low-salt (LS) or hi
gh-salt (HS) diets, and RRM-HT rats were fed HT diet for 4-6 weeks. In situ
and isolated cremaster muscle first-order arterioles (1A) were examined us
ing television microscopy, and a video micrometer was used to measure diame
ter changes in response to acetylcholine (ACH), cholera toxin (CT), and sod
ium nitroprusside (SNP).
Results: Compared to normotensive low-salt (NT-LS) rats, responses of 1A to
the agonists were reduced in normotensive high-salt (NT-H) and RRM-HT rats
. Arteriolar reactivity to the agonists in NT-LS rats and in NT-HS rats was
not different between in situ and in vitro environments. However, in RRM-H
T rats, the reactivity of 1A to each agonist was greater in isolated arteri
oles than in in situ arterioles.
Conclusions: These results suggest that the impaired response of skeletal m
uscle arterioles to vasodilator stimuli in normotensive rats on high-salt d
iet primarily reflects alterations to microvessels alone, while reduced dil
ator responses in RRM-HT rats represent a combination of extravascular infl
uences and intrinsic alterations to arterioles themselves.