Catecholamine-induced polyploidization in vascular smooth muscle cells.

Polyploidy formation of vascular smooth muscle cells was observed in vivo by intravenous infusion of norepinephrine or epinephrine in Wistar-Crea rats for 12 days at the rate of 0.02 mumol/hr with an osmotic minipump and in vitro by exposing cultured vascular smooth muscle cells obtained from normotensive Wistar-Kyoto rats (WKY) and spontaneously hypertensive rats (SHR) to norepinephrine (10(-7)M to 10(-5)M) in the cultured medium. Infusion in vivo of norepinephrine but not epinephrine increased blood pressure slightly. However, both agents increased significantly the frequency of tetraploidy of smooth muscle cells up to 14.9 +/- 0.6% (mean +/- SE) and 9.2 +/- 0.5% compared with saline (6.5 +/- 0.7%). Exposure in vitro to norepinephrine (10(-6)M) increased the frequency of tetraploidy and octaploidy of smooth muscle cells from SHR up to 14.2% and 2.1%, respectively, compared with nonexposed cells (8.1% and 0.2%). These results appear to indicate that norepinephrine and epinephrine induce polyploidy of smooth muscle cells independently from blood pressure elevation.