AJP - Heart and Circulatory Physiology, Vol 243, Issue 2 243-H251, Copyright © 1982 by American Physiological Society
Development of microvascular rarefaction in the spontaneously hypertensive rat
R. L. Prewitt, I. I. Chen and R. Dowell
Using stereological methods in vivo, we have investigated the rarefaction
of arterioles and capillaries in male spontaneously hypertensive rats (SHR)
and the Wistar-Kyoto controls (WKY) at 6-8, 12-14, and 16-18 wk of age.
Under chloralose-urethan anesthesia, the gracilis muscle was isolated for
microscopic observation. Vessel length and surface area per unit volume of
tissue (density) were determined during three consecutive states:
innervation, denervation, and vasodilation with nitroprusside. Arteriolar
wall-to-lumen ratio was measured after vasodilation. At 6-8 wk capillary
density was reduced in the SHR. At 12-14 wk there was a reduction of
arteriole and capillary density under innervated and denervated conditions
but not after vasodilation (a state of functional rarefaction). At 16-18 wk
there was a reduction of arteriolar and capillary density under all three
conditions (a state of anatomical rarefaction). At 12-14 and 16-18 wk there
was an elevated level of arteriolar vasoconstriction in the SHR that was
masked in any one state by the closure of the smaller arterioles.
Arteriolar wall-to-lumen ratio was not elevated in the SHR at any time.
Arteriolar closure was not reversed by acute denervation.
