AJP - Heart and Circulatory Physiology, Vol 256, Issue 1 213-H221, Copyright © 1989 by American Physiological Society
Attenuated microvascular alterations in coarctation hypertension
D. L. Stacy and R. L. Prewitt
Department of Physiology, Eastern Virginia Medical School, Norfolk 23501.
Arteriolar vasoconstriction, structural reductions in dilated diameter, and
rarefaction have been observed in vascular beds with chronic renal
hypertension. To determine their pressure or flow dependence, these
functional and structural parameters were studied in the developing and
chronic stages of coarctation hypertension in the cremaster muscle, a
normotensive skeletal muscle bed that is protected from the effects of
elevated microvascular pressures. Hypertension was produced in rats by
placing a silver clip around the abdominal aorta above the branches of the
renal arteries. In hypertensive rats, resting diameters were reduced in
second-order arterioles after 4 and 8 wk, in third-order arterioles after
2, 4, and 8 wk, and in fourth-order arterioles after 4 and 8 wk, vs.
controls. Vascular tone was elevated in second-order arterioles after 2, 4,
and 8 wk and in third- and fourth-order arterioles after 8 wk in
hypertensive rats. No increases in medial-intimal area were found at any
stage of hypertension in any arteriolar order. The density of small
arterioles (3rd-5th orders) was reduced by 20% in hypertensive rats at 8 wk
but was unchanged at the other time periods. These arteriolar alterations,
especially the absence of structural reductions in diameter, are attenuated
compared with those observed in one-kidney, one-clip hypertension and
suggest that most of the arteriolar alterations that occur in renal
hypertension are pressure or flow dependent.
