A perfusion-fixation and vascular casting technique was used to assess the effects of acute, angiotensin-induced hypertension on the intrarenal arteries and, for comparison, the small arteries of the intestine. The first objective was to establish that the technique accurately preserves postmortem the vascular changes induced by acute hypertension. To do this, the easily accessible intestinal arteries were examined and photographed both in vivo and after fixation and injection of Batson's no. 17 casting resin in a group of angiotensin-treated rats and controls. The second objective was to apply the technique to observe and compare acute hypertensive changes in the intrarenal and intestinal arteries; studies included scanning electron microscopy of vascular casts and transmission electron microscopy of vessel walls using ferritin as a tracer to assess permeability. In the angiotensin-treated rats, casts or both intrarenal and intestinal arteries showed many well-defined zones of constriction and nonconstriction. Transmission electron microscopy of both the smaller interrenal (interlobular) arteries and intestinal vessels revealed focal smooth muscle rarefaction and abnormal permeability to ferritin, found only in the nonconstricted zones. This study provides new evidence that in the kidney, as in the intestine, acute hypertension produes a characteristic pattern of arterial constriction and nonconstriction, and that hypertensive vascular lesions with accompanying increased permeability occur exclusively in the nonconstricted zones.
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