Differential effect of renal wrap hypertension on aortic smooth muscle polyploidy in the rat and rabbit

1. The incidence of aortic smooth muscle cell polyploidy was investigated in rabbits and rats with renal wrap induced (cellophane perinephritic) chronic hypertension. 2. Bilateral renal cellophane wrapping was performed in young adult animals. Blood pressure was measured intra-arterially in the rabbits twice during the experimental period and tail-cuff blood pressure measured twice weekly in the rats. At 8 weeks post-surgery the incidence of aortic smooth muscle cell polyploidy was determined in enzymatically isolated cells by flow cytometric DNA analysis. 3. Systolic blood pressure was significantly increased in the bilateral renal wrapped rabbits and rats compared to the shams, such that at 8 weeks post-surgery, systolic blood pressure was 139 +/- 2 mmHg and 84 +/- 2 mmHg, respectively, in the rabbits and 188 +/- 6 mmHg and 155 +/- 4 mmHg, respectively, in the rats. 4. The incidence of polyploid smooth muscle cells was significantly higher in the hypertensive renal wrapped rat compared to the sham (20.9 +/- 1.5% and 8.1 +/- 0.5%, respectively). However, the incidence of polyploid cells was low in the rabbit aortae with no significant difference in the incidence of aortic smooth muscle polyploidy in the hypertensive rabbit compared to the sham (2.6 +/- 0.6% and 2.7 +/- 0.6%, respectively). 5. This study demonstrates a species difference in the induction of polyploidy during the same model of experimental hypertension in aortic smooth muscle derived from the rabbit and rat.