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Role of polyamines in hypertension induced by angiotensin II
J Ibrahim1, M Schachter, A D Hughes
1Department of Clinical Pharmacology, St Mary's Hospital Medical School, London, United Kingdom.
Objective:
The aim was to investigate the involvement of polyamines in the development of cardiovascular hypertrophy in a rat angiotensin II infusion model of hypertension.
Methods:
Rats were chronically infused with a low dose of angiotensin II (83 ng.min-1.rat-1) or vehicle by osmotic minipumps. The polyamine content of the cardiovascular organs and liver was measured by HPLC, and the blood pressure of conscious rats was determined by a tail cuff method. The mesenteric arterial beds were perfusion fixed in situ and medial and luminal cross sectional areas were determined by computer assisted planimetry. Cardiac hypertrophy was assessed by determination of ventricular:body weight ratios.
Results:
Angiotensin II infusion caused an increased concentration of polyamines in the ventricles and aorta within hours of beginning the infusion, and within days in the mesenteric arteries. Polyamine content of the liver was unaffected. Hypertrophy of the myocardium and mesenteric arteries in association with the increased blood pressure was evident.
Conclusions:
A low dose of angiotensin II stimulates an early biochemical marker of growth, the polyamines, in cardiovascular tissues but not in the liver. The increase in tissue polyamines is associated with cardiovascular hypertrophy and the development of hypertension.