Blockade of the renin-angiotensin system (RAS) prevents the increase in blood pressure (BP) induced by chronic administration of
NG-nitro L-arginine methyl ester (
L-NAME) in rats. In the present study, we showed how a converting
enzyme inhibitor can prevent the end-stage tissue damage due to chronic
nitric oxide (
NO) synthase blockade and thus improve the survival rate. Three experiments were performed. In the first, rats (n = 10) were given
L-NAME (50 mg/kg) and 10 other rats were given
L-NAME plus
quinapril (10 mg/kg) starting 1 month after
L-NAME administration. Ten untreated rats were used as controls. Rats were killed after 2 months, and the RAS, renal function, and renal morphology were analyzed. In the second experiment, a similar protocol was used, and function and morphological damage in renal slices and cervical medullary tissue were assessed after 4 months of
L-NAME and 3 months of
quinapril +
L-NAME. In the third experiment, a similar protocol was used, but to establish survival curves, the animals were not killed.
L-NAME significantly increased BP without causing any significnat changes in plasma
renin activity (PRA) at 2 months. The aortic wall
cyclic GMP content was significantly decreased, and the
angiotensin-converting enzyme (ACE) activity was increased by
L-NAME.
Quinapril significantly reversed the high BP induced by
L-NAME without changing the decrease in the aortic wall
cyclic GMP. Two-month
L-NAME treatment decreased renal function and damaged renal tissue.
Quinapril prevented both
proteinuria and morphological damage. Four-month
L-NAME treatment induced renal end-stage damage and
infarctions of the cervical medulla.
Quinapril prevented this end-stage damage in the kidney and cervical medulla.
Quinapril therefore prevented the increased mortality due to
L-NAME. Hence, inhibition of ACE, despite its lack of effect on arterial wall
cyclic GMP, does reverse the
hypertension and prevent end-stage vascular damage induced by chronic
L-NAME in target organs.