Effect of long-term treatment with propionyl-L-carnitine on smooth muscle cell polyploidy in spontaneously hypertensive rats

Experimental studies suggest that DNA content is increased in the smooth muscle cells of the arteries of hypertensive animals. It is unclear whether an increase in DNA content occurring in the smooth muscle cells of hypertensive rats represents a pressure-dependent effect. To evaluate the antihypertensive effect of long-term treatment with propionyl-L-carnitine and the possible morphological changes in thoracic smooth muscle cells correlated with this effect, we studied 4-month-old spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY) randomly divided into five groups. One group of SHR was treated with propionyl-L-carnitine for 12 months; the other four groups of SHR and WKY received no treatment and were controls. We used static and flow cytometry to evaluate the polyploid cell content in thoracic aorta smooth muscle cells. Systolic pressure in untreated SHR progressively increased during the experiment. Treatment did not significantly influence pressure values in SHR. In WKY, blood pressure was significantly lower than that in treated and untreated age-matched SHR (2P < .02). The number of polyploid smooth muscle cells was significantly lower in the propionyl-L-carnitine-treated SHR than in the untreated rats (2P < .04) and similar to values for WKY. The reduction of polyploid cells in treated SHR was paralleled by a significant decrease of the aortic total DNA content, whereas no modifications occurred in smooth muscle cell mass. Long-term treatment with propionyl-L-carnitine may interfere with cellular mechanisms regulating the secondary responses involved in DNA synthesis.