VASCULAR COMPLIANCE IN SODIUM-SENSITIVE AND SODIUM-RESISTANT BORDERLINE HYPERTENSIVE PATIENTS

Recently, we demonstrated a reduction in the compliance of the carotid , femoral and brachial arteries in sodium-sensitive subjects who had c onsumed a regular sodium intake of approximately 120 mmol per day, as compared to both sodium-resistant borderline hypertensive subjects and normotensive controls. Venous compliance was not different between th e two borderline hypertensive groups and was only slightly lesser than in controls. Large artery compliance was studied using a non-invasive ultrasound vessel wall movement detector system, while venous complia nce was determined by means of strain gauge plethysmography. The borde rline hypertensive subjects were subsequently treated with enalapril 1 0 mg/day, felodipine 5 mg/day or placebo during six months. Despite si milar reductions in blood pressure, enalapril induced a significant in crease of the muscular femoral and brachial artery compliance, but not of the elastic carotid artery, while felodipine did not influence lar ge artery compliance at all in the sodium-sensitive group. The effect of enalapril on muscular artery compliance was established through a d ose-dependent increase in distension and not through a change in arter ial diameter. Arterial compliance was not influenced by either of the drugs in the resistant group. Venous compliance was also not altered b y the medication. In conclusion, femoral and brachial artery complianc e in sodium-sensitive borderline hypertensive subjects, which was foun d to be lower than that of sodium-resistant subjects, improved with an tihypertensive treatment with enalapril but not with felodipine, despi te the similar reductions in blood pressure induced by both drugs. Thi s finding implies that firstly, reduced arterial compliances caused by more than just blood pressure elevation, and secondly, the renin-angi otensin system may play a role in the reduced arterial compliance of s odium-sensitive subjects.