Methods Eight pregnant Sprague-Dawley rats were used in the present study. In order to avoid hormonal influence, only male rat pups were included and sacrificed randomly on Day of Life 1, 7, 14 and 28. Brain, kidney and heart organs were removed and homogenized in buffer to study the expression of ETA and ETB receptor protein levels using western blot technique.
Results The mean body weight, brain, kidney and heart weights increased proportionally with advancing age showing adequate nutrition and growth. The behavioral development of rats during the observational period was normal. The expression of ETA receptors in the brain, heart and kidneys was similar in rats of postnatal ages 1, 7, 14 and 28 days. However, ETB receptor expression significantly (p<0.001) decreased by 72 % on day 28 compared to rats of age 1, 7 and 14 days. Conclusions: These results demonstrate that ETB receptor expression is higher in neonatal rat brain on day 1 through 14 of life and decreases with age (day 28). No change in expression of ETA receptors was observed. No change in either ETA or ETB receptor expression was observed in the heart or kidney suggesting that ET receptors have a more functional role in these organs than a developmental one. We conclude that ETB receptor ontogeny decreases with age in the brain implicating its involvement in the development of the central nervous system.
Conclusion These results conclusively demonstrate for the first time that expression of ETB receptors were higher in the neonatal rat brain (age: day 1, and 14) and the expression was decreased with age (day 28). These results signify that ETB receptors may have a significant role in the brain development. No significant change in receptors density was observed on hearts and kidneys.