Augmented vasoconstrictor response to changes in vascular transmural pressure in patients with essential arterial...

The vasoconstrictor response to increase in venous transmural pressure in subcutaneous tissue was studied in 9 patients with essential arterial hypertension. Subcutaneous blood flow was measured on the distal part of the forearm and at the lateral malleolus by the local 133Xe washout technique. Increase in venous transmural pressure was obtained by lowering the area under study 40 cm below midaxillary line in the recumbent subject. Average mean arterial pressure +/- 1 S.E. was 133 +/- 6 mmHg. The fractional increase in vascular resistance induced by arteriolar constriction was more pronounced in the hypertensive patients that in a normotensive control group. "Minimal vascular resistance" in the papaverine relaxed vascular bed was higher in the hypertensive patients than in the controls. Distensibility of the papaverine relaxed resistance vessels was diminished in the patients. Follow-up studies after 6-18 months of anti-hypertensive treatment indicate that the vasoconstrictor response as well as "minimal vascular resistance" are normalized, whereas the distensibility of the papaverine relaxed arterioles remained unaltered in the hypertensive patients. The results indicate that the arteriolar smooth muscle cells of hypertensive patients are subjected to reversible hypertrophy whereas the reduced distensibility of the resistance vessels is due to irreversible structural changes.