Attenuation in rat brain nitric oxide synthase activity in the coarctation model of hypertension

The correlation of brain nitric oxide synthase (NOS) activity with renal hypertension has been investigated in rats. NOS activity was measured by oxyhaemoglobin and by conversion of radioactive arginine to citrulline. There was significant elevation of blood pressure (54% increase) along with left ventricular hypertrophy (26% greater than the control) 8 weeks after coarctation. The brain NOS activity was also significantly reduced in coarctated animals (45% of the control value). Treatment with captopril (angiotensin converting enzyme inhibitor) or centhaquin (centrally acting antihypertensive agent) led to significant reduction of left ventricular hypertrophy and a marked recovery in the brain NOS activity (to 92% and 135% of the control, respectively). Nifedipine (a calcium channel blocker) also brought about normalization of blood pressure but the left ventricular hypertrophy was not prevented. The brain NOS activity in the nifedipine treated group also showed a significant trend of recovery (to 73% of the control NOS activity). The results suggested that there is an inverse correlation between brain NOS activity and blood pressure level.