1. Continuous intravenous noradrenaline infusion for 1 week into rats by osmotic minipumps significantly increased blood pressure and left ventricular weight.

2. Concomitant α-receptor-blockade infusion significantly lowered blood pressure and the aortic weight without significant reduction in left ventricular weight.

3. Two β-receptor-blocking agents in noradrenaline-infused rats normalized left ventricular weight and significantly reduced the aortic weight, although blood pressure was still higher than control non-infused rats.

4. In 7-week-old spontaneously hypertensive rats, propranolol (perorally for 2 weeks) did not lower blood pressure but reduced significantly cardiovascular protein synthesis ([14C]lysine and [3H]uridine incorporation into non-collagen protein and RNA respectively) in both left ventricle and aorta. This effect was in contrast to hydrallazine, which normalized blood pressure but did not reduce cardiovascular protein synthesis.

5. Results suggest that β-receptors play a modulating role in the structural cardiovascular response to blood pressure.

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