Morphology of the intestinal arterioles in chronic human hypertension.

Abstract

The wall/lumen ratio, cross-sectional area of wall, and caliber of the arterioles in the wall of the small intestine have been studied in 6 chronic hypertension and 6 normotensive cases, following injection of the superior mesenteric artery with a suspension of bismuth oxychloride in gelatin at a pressure of 150-250 mm Hg. The hypertensive cases were generally injected at a somewhat higher pressure than the controls. The aim of the injection was to distend all arterioles down to a diameter of 20 [mu] and so abolish the variable degree of post-mortem contraction that is present in uninjected specimens. In all the cases studied, the undulation of the internal elastic lamina was completely abolished. The wall/lumen ratio of the arterioles was found to be increased in cases of hypertension, as reported in studies on uninjected tissues, but there was no increase in cross-sectional area of the arteriolar wall; meaning no hypertrophy or hyperplasia. Measurements of arteriolar caliber confirmed that the increase in wall/lumen ratio was due to a decreased arteriolar diameter. The evidence suggests that in chronic hypertension there is a persistent shortening of the circular elements in the arteriolar wall. This abnormality could conceivably be congenital, but more likely is a result of prolonged arteriolar constriction in the early stages of hypertension. Once developed, it would probably become an important factor in maintaining the raised blood pressure. Because of the analogy with the myostatic contractore of skeletal muscle, this condition may provisionally be termed arteriolar contracture.