Effect of pressure overload on angiotensin receptor expression in the rat heart during early postnatal life

The development of cardiac hypertrophy during neonatal life and in adults i mplies different processes. The angiotensin TI (Ang II) system is involved in the development of cardiac hypertrophy in adults, but its role in neonat es remains unclear. The aim of this study was to estimate the influence of increased hemodynamic load on the developmental pattern of the AT1/AT2 rece ptor expression in the heart. Two-day-old rats submitted to abdominal aorti c constriction IAC) or sham operation were sacrificed 2 hi and 1, 3, and 8 days after surgery. Ang II was evaluated in sera and immunohistology was pe rformed to define the cardiac hypertrophy process. The Ang II receptor subt ypes I and 1 were quantified at the receptor and mRNA levels by I-125-Ang I I binding and RT-PCR, respectively Ang II content in sera increased transie ntly 2 h after surgery in the AC group. In sham-operated, AT1 and AT2 decre ased throughout the period studied at both mRNA and receptor levels. Howeve r, the AT1 mRNA level decrease was more pronounced than that of AT2 (by 57% and 27%, respectively). AC not only prevented the postnatal decrease in AT mRNA level but resulted in an increase in AT1 mRNA 8 days after surgery (P <0.05). Besides in the AC groups, AT2 mRNA levels but not those of AT1 mRNA were linearly correlated with the left ventricular mass. At the receptor l evel, a significant transient (1 day after surgery) increase in both AT1 an d AT2 was observed. In conclusion, our data demonstrated that imposition of pressure overload soon after birth altered the pattern of AT receptor expr ession. (C) 2000 Academic Press.