LONG-TERM NO SYNTHASE INHIBITION AFFECTS HEART-WEIGHT AND GEOMETRY OFCORONARY AND CAROTID ARTERIES

The heart weight and the structure of coronary and carotid arteries we re studied in NO-deficient hypertension. Wistar rats were administered L-NAME (50 mg/kg/day) in drinking water for a period of 8 weeks. The blood pressure and heart rate were recorded weekly. In one group of co ntrol and experimental animals the heart weight was assessed and the h eart/body weight ratio (relative heart weight) was calculated. In the other group of control and experimental animals, the cardiovascular sy stem was perfused by a fixative under constant perfusion pressure. The inner circumference and the wall thickness (tunica intima and tunica media) of the coronary (septal branch) and carotid artery were measure d using light microscopy and the wall/diameter ratio was calculated. I nhibition of NO synthase induced a significant increase in blood press ure (187.2+/-4.2 mm Hg compared to 131.4+/-1.9 mm Hg in the controls, p<0.01). The heart rate decreased (334.4+/-7.0 beats/min compared to 3 52.6+/-4.1 beats/min in the controls, p<0.05). The heart weight increa sed in NO-deficient rats (132+/-0.08 g versus 1.10+/-0.03 g, p<0.05); the heart/body weight index increased remarkably (3.09+/-0.15 compared to 2.10+/-0.04 in the controls, p<0.01). Morphometry of the septal br anch of the left coronary artery indicated a decrease of the inner cir cumference (664+/-24 mu m versus 832+/-30 mu m, p<0.01), the increased wall thickness (21.15+/-0.84 mu m compared to 12.47+/-0.62 mu m in th e controls, p<0.01) and the remarkably changed wall/diameter ratio (1: 10 versus 1:21 in the controls). Similar alterations were found in the carotid arteries: the inner circumference was decreased (2456+/-39 mu m versus 2732+/-66 mu m, p<0.01), the wall thickness increased (45.14 +/-0.41 mu m compared to 26.08+/-1.23 mu m, p<0.01) and the wall/diame ter ratio was changed to 1:17 in comparison with 1:33 in the controls, In conclusion, cardiac hypertrophy and structural alterations of the coronary artery and carotid artery accompany NO-deficient hypertension .