[Proliferation of smooth muscle cells in hypertension]

The aortic intima and media isolated from hypertensives showed a significantly larger number (up to 20%) of smooth muscle cells (SMC) with tetraploid DNA content. The similar process was shown to be also a part of normal human vessel maturation. Normotensive human and rat aortic SMCs were found to accumulate 3H-thymidine, have a lower proliferative ability and they were apt to polyploidize in the primary culture. Such a population could not be detected in the aorta of spontaneously hypertensive rats. It was ascertained that 10 microM of noradrenaline significantly increased (approximately by 2 times) the occurrence of true polyploid cells in the rat aortic SMC subculture. The effect of noradrenaline was blocked by the concomitant effects of alpha- and beta-adrenoreceptor antagonists. SMC polyploidization was also stimulated by the simultaneously use of the direct activators of second messenger systems forskolin and phorbol-12-myristate-13-acetate. Thus, the SMC subpopulation that is apt to polyploidize exists in normal vessels and noradrenaline may be one of the mediators of a response of the vascular wall SMC, which seems to occur due to the synergism of two second messenger systems.