Ultrastructural Changes in Mesenteric Arteries from Spontaneously Hypertensive Rats

Lee, R.M.K.W.; Forrest, James B.; Garfield, R. E.; Daniel, E. E.

doi:10.1159/000158461

Cited by 48 publications

(56 citation statements)

References 16 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…9 '" Lombard et al 9 also found the greatest dilation in the region of the third-order (A3) arterioles (which are close to the transverse arterioles in our terminology) and attributed the effect to a higher neural transmission and more vigorous responses to oxygen. These observations are compatible with the greater density of nerve plexes in arterioles of SHR 20 and an elevated central sympathetic nerve activity. 21 The fact that the degree of vascular tone varies considerably along individual pathways in the arterioles may suggest that such an elevated nerve activity is not transmitted uniformly along the arteriolar tree.…”

Section: Previous Studiessupporting

confidence: 85%

Microvascular tone in a skeletal muscle of spontaneously hypertensive rats.

Schmid‐Schönbein

Zweifach²,

DeLano³

et al. 1987

Hypertension

View full text Add to dashboard Cite

SUMMARY We studied the degree of arteriolar smooth muscle constriction in the spinotrapezius muscle microcirculation of spontaneously hypertensive rats and their normotensive controls, WistarKyoto rats. The constriction was expressed in the form of a nondimensional tone as the difference between steady state and dilated diameter (after papaverine treatment) divided by the dilated diameter. Both animal strains showed on average a progressive increase of tone toward the more distal arterioles, with a peak tone being reached in the transverse arterioles. Tone values in the hypertensive animals were consistently elevated. The number of arterioles that had more than 5% tone (so-called responder arterioles) was higher in the hypertensive animals. These studies suggest that, besides the anatomical adjustments documented earlier in our laboratory in the arteriolar network of this muscle, functional adjustments in the form of an elevated microvascular tone are associated with the elevated resistance in spontaneously hypertensive rats. (Hypertension 9: 164-171, 1987) KEY WORDS • tone skeletal muscle arteriole • spontaneous hypertension • microcirculation O UR earlier studies of the microcirculation dealing with the spontaneous form of hypertension in rats 1 showed that resistance is increased across the hierarchy of precapillary arterioles, as evidenced by the altered pressure-flow relationships in consecutive segments of the spinotrapezius muscle bed. There are, however, insufficient data concerning the factors responsible for such alterations. Previous workers advanced the so-called rarefaction concept of hypertension 2 when they found that there was no statistically significant decrease in the diameter of comparable arterioles in order to account for the above-normal microvascular resistances in spontaneously hypertensive rats (SHR). Experimental data in support of arteriolar rarefaction have been advanced for the cremaster 2 and anterior gracilis muscle preparations 3 of SHR and for the renal form of hypertension. 4 Few of the studies in the literature have estimated microvascular resistance levels on the basis of direct measurements of pressure and flow in the various sections of the network. Our own studies of the problem in

show abstract

Section: Previous Studiessupporting

confidence: 85%

Microvascular tone in a skeletal muscle of spontaneously hypertensive rats.

Schmid‐Schönbein

Zweifach²,

DeLano³

et al. 1987

Hypertension

View full text Add to dashboard Cite

show abstract

“…25 " 28 Several authors have suggested that smooth muscle cell hypertrophy may be a primary abnormality preceding the development of hypertension. Moreover, in SHRs the increase in stiffness of the arterial wall could participate in hemodynamic alterations.…”

Section: Discussionmentioning

confidence: 99%

Effect of a nonhypotensive long-term infusion of ANP on the mechanical and structural properties of the arterial wall in Wistar-Kyoto and spontaneously hypertensive rats.

Grand

Poitevin

Benessiano

et al. 1993

Arterioscler Thromb

View full text Add to dashboard Cite

A nonhypotensive dose of atrial natriuretic peptide (ANP) was infused (60 pg/kg body wt per day s.c. by osmotic pump) for 25 days in 16-week-old normotensive Wistar-Kyoto rats (WKYs, TI = 12) and age-matched spontaneously hypertensive rats (SHRs, n = 12). During the infusion period, systolic blood pressure, urinary volume, and cyclic guanosine monophosphate (cGMP) excretion/12 hr were measured once a week in both groups. Then mechanical and morphological properties of the arterial wall and plasma ANP levels were assessed and compared with those from control groups of SHRs («=8) and WKYs (n=8) receiving a saline vehicle. The compliance (CC) of the in situ localized carotid artery was measured for pressures ranging from 25 to 175 mm Hg under control conditions and after "poisoning" of smooth muscle tone by potassium cyanide. After pressure fixation, the medial thickness, elastin and collagen contents, and the size and number of nuclei were measured in the thoracic descending aorta. In WKYs, ANP did not modify either mechanical or structural properties of the arterial wall or biochemical parameters. Conversely, in ANP-treated SHRs, CC was significantly increased compared with untreated SHRs under basal conditions (p<0.03) and after potassium cyanide poisoning (/><0.02). Structural properties were also modified by ANP in SHRs, i.e., medial thickness (129.3±4.1 versus 113.1 ±3.3 jum, p<0.01) and nuclear size (8.81 ±0.28 versus 5.52±0.20 /i.m\p<0.0001) in untreated and treated SHRs, respectively. Furthermore, urinary volume and cGMP content were significantly increased during ANP infusion in treated SHRs (p<0.05). The present results indicate concomitant modifications of mechanical and structural properties of the arterial wall in SHRs chronically treated with low doses of ANP. These long-term effects of ANP could be involved in the remodeling of the arterial wall observed during hypertension and could have beneficial effects on cardiovascular diseases in chronic sustained hyperten- fects such as an increase of diuresis, natriuresis, J. JL urinary excretion of cyclic guanosine monophosphate (cGMP), and glomerular filtration rate and a selective regional relaxation of vascular smooth muscle cells 1 that is partially mediated by the activation of particulate guanylate cyclase via its second messenger, cGMP. The vasorelaxant effects of ANP have been extensively demonstrated in in vitro preparations 2 -4 but not so much in in vivo models. Recent studies have demonstrated that long-term infusion of ANP at low doses reduces blood pressure in several animal models of hypertension, including spontaneously hypertensive rats (SHRs). 5 -8 In this strain, it has been previously shown that the antihypertensive properties were more Received August 13, 1992; revision accepted October 30, 1992. marked when the plasma levels of ANP were modestly but chronically elevated than when they were markedly and acutely increased. 8In SHRs, elevated systemic resistances are associated with an increase in arteriolar and arterial wall thickne...

show abstract

“…32 In these vessels, increase in medial wall size is mainly due to hyperplasia of the smooth muscle cells. 33 As discussed above, angiotensin II is known to induce hypertrophy and not hyperplasia of vascular smooth muscle cells. It is also unlikely that prevention of vascular changes in this type of artery was secondary to the prevention of hypertension by captopril because long-term treatment of SHR with vasodilators, although it normalized the blood pressure, was not sufficient to alter the vessel wall dimensions in the renal 20 and mesenteric 34 vascular beds.…”

mentioning

confidence: 96%

Prevention of hypertension and vascular changes by captopril treatment.

et al. 1991

View full text Add to dashboard Cite

Treatment of female spontaneously hypertensive rats (SHR) and control Wistar-Kyoto (WKY) rats with captopril was carried out by the addition of the drug in the drinking water throughout pregnancy and lactation and after weaning. At 28 weeks of age, average systolic blood pressure of treated SHR was 113±3 mm Hg, which was below that of control SHR (188±3 mm Hg) and WKY rats (124±3 mm Hg). Body weight and heart rate of the SHR were not affected by the treatment Tissue level of catecholamines was increased by captopril treatment in the superior cervical ganglia but remained unchanged in the plasma, heart, mesenteric arteries, and the adrenal glands of both SHR and WKY rats. Left ventricular weight, wall thickness, and internal diameter of the left ventricle in the SHR were reduced by the treatment Morphometric measurements of the mesenteric arteries showed that vascular alterations present in the control SHR were prevented by the treatment In the superior mesenteric artery and large mesenteric artery, smaller lumen size at maximal relaxation found in the control SHR was normalized to the level of the WKY rats. Hypertrophy of the medial wall in the superior mesenteric, large and small mesenteric arteries, and an increase in the number of smooth muscle cell layers in the large mesenteric artery of the SHR were prevented by the treatment. Perfusion study of the mesenteric vascular bed showed that reactivity of these vessels to norepinephrine was reduced, and sensitivity to norepinephrine (as determined by the effective dose that causes 50% of maximal response) was increased in the SHR by captopril treatment Sensitivity of the tail artery in response to norepinephrine was not altered by the treatment We conclude that long-term treatment with captopril of SHR before and after birth prevented the development of hypertension, structural and functional alterations of the mesenteric arteries, and cardiac hypertrophy. (Hypertension 1991;17:141-150) C hronic intracerebroventricular administration of captopril, when started in young spontaneously hypertensive rats (SHR), has been shown to attenuate the development of hypertension in these animals. -2 Such an effect was associated with a marked depression in vascular reactivity to exogenous vasoconstrictors and a potentiation of baroreceptor

show abstract

Ultrastructural Changes in Mesenteric Arteries from Spontaneously Hypertensive Rats

Cited by 48 publications

References 16 publications

Microvascular tone in a skeletal muscle of spontaneously hypertensive rats.

Microvascular tone in a skeletal muscle of spontaneously hypertensive rats.

Effect of a nonhypotensive long-term infusion of ANP on the mechanical and structural properties of the arterial wall in Wistar-Kyoto and spontaneously hypertensive rats.

Prevention of hypertension and vascular changes by captopril treatment.

Contact Info

Product

Resources

About