ALTERED BALANCE BETWEEN CELL REPLICATION AND APOPTOSIS IN HEARTS AND KIDNEYS OF NEWBORN SHR

Apoptosis is involved in neonatal remodeling of organs of the cardiova scular system. Since are previously reported hyperplasia of these orga ns al birth in several forms of genetic hypertension, the aim of this study was to determine whether alterations of the apoptotic process co uld explain our findings. The heart, aorta, and kidneys of newborn Wis tar-Kyoto and spontaneously hypertensive rats were harvested 24 hours after an injection of [H-3]thymidine. DNA was extracted to measure its specific activity (index of DNA synthesis) and DNA fragmentation as a n estimation of apoptosis. All organs studied showed an increased weig ht to body weight ratio in spontaneously hypertensive rats. Twenty-fou r hours after birth, DNA synthesis in all organs of spontaneously hype rtensive rats was comparable to that in normotensive rats. However, ap optosis was markedly decreased In the heart and kidneys of newborn spo ntaneously hypertensive rats compared with their normotensive controls . In the aorta, apoptosis was reduced, but not significantly. Calculat ion of a proliferation index (DNA synthesis/fragmentation) revealed a significant increase of heart proliferation, with a similar trend in t he aorta and Kidneys. In addition, we found a negative correlation bet ween heart weight and DNA fragmentation. Although other factors may in fluence hyperplasia of the aorta, we propose that a reduction of apopt otic activity is responsible, at least in part, for heart and kidney h yperplasia in newborn spontaneously hypertensive rats.