Naturally Occurring Intrauterine Growth Retardation and Adult Blood Pressure in Rats

In humans, infants who are born small have been reported to have higher blood pressure in adulthood than do larger infants. This suggests that factors in the intrauterine environment that affect fetal growth can program the individual for hypertension later in life. The present study determined whether there is a similar, naturally occurring relationship between birth weight and adult blood pressure in rats. Female Sprague-Dawley rats bred in our colony were fed a normal diet during pregnancy. On the day of delivery, any pups that weighed <90% of the mean pup weight for the litter were identified as runts. For each runt, a sex-matched littermate of normal weight was also identified and assigned to this study. These pairs were chronically instrumented at ∼20 wk of age. Mean arterial pressure was significantly higher in runt male and female offspring compared with their normal birth weight littermates (males: 149 ± 7, runts versus 129 ± 4 mm Hg, controls; females: 128 ± 1, runts versus 119 ± 2 mm Hg, controls). Although the runts had smaller body weights at study than did their littermate controls, the kidney-to-body weight ratio and renal function normalized to kidney or body weight were not different. These studies indicate that adult blood pressure is related to birth weight in rats, as it is in humans. The relative hypertension in runt animals is not due to gross differences in renal function but may be related to more subtle renal structural and/or functional differences.