1. The present study was designated to determine whether there are any detectable differences in cardiovascular anatomy or physiology between Wistar-Kyoto (WKY) and spontaneously hypertensive rat (SHR) pups at birth.
2. It was found that mean arterial pressures were significantly higher, heart rates were slightly higher, and heart weight/body weight ratios were higher in SHR.
3. Vascular dimensions were determined in a small sample of those rats, and the data there also indicate hypertrophy to some degree: the ratio of wall thickness/lumen radius was higher in SHR, tangential wall tension and number of cell layers in the media were increased.
4. It is concluded that some of the concomitant features of hypertension, such as left ventricular wall hypertrophy and arterial wall hypertrophy, may be genetically determined to some extent in SHR.