Body weight of the spontaneously hypertensive rat during the suckling and weanling periods.

The body weight of the spontaneously hypertensive rat (SHR) during the suckling, birth to 3 weeks of age, and weanling period, through 6 weeks of age, is compared to that of its normotensive controls, the Wistar Kyoto (WKY) and Wistar (WR) rats. Litters were normalized to 6 pups per dam just after birth. The WR is larger than the SHR and WKY at all time points examined. The WKY is similar in weight to the SHR at birth but larger than the SHR at the other time points studied. These findings suggest the WR is inherently a larger rat than the SHR and WKY during the suckling and weanling periods while the development of a weight difference between the SHR and WKY after birth suggest an extrauterine influence.