Angiotensin II Type 2 Receptor mRNA Expression in the Developing Cardiopulmonary System of the Rat

Abstract

Recent studies have shown that angiotensin II has a trophic action on the heart. The presence of two types of angiotensin II receptors, type 1 (AT1) and type 2 (AT2), has been reported in the rat heart. This in situ hybridization study describes the tissue and cell location of AT2 receptor mRNA in the developing rat cardiopulmonary system, from 15 days of gestation to adulthood. Expression of AT1A receptor mRNA was studied in parallel for direct comparison. The aortic arch and pulmonary artery expressed high levels of AT2 receptor mRNA from 15 days of gestation up until 15 days postpartum, whereas expression of this mRNA was observed only just before and after birth in the coronary arteries. AT2 receptor mRNA was not detected in any cardiac muscle of the fetus, neonate, or adult. The annulus of all four heart valves expressed AT2 mRNA from 21 days of gestation until 10 days postpartum, but no labeling was seen in the valve leaflets. The subendocardial atrial tissue showed a high level of AT2 receptor mRNA expression during the early postnatal period, but no expression was observed in the atrial myocytes from fetal stages to adulthood. The bronchi and trachea, but not the lung parenchyma, showed a high level of AT2 receptor mRNA expression starting from 17 days of gestation until 10 days postpartum. AT2 receptor mRNA expression in the cardiopulmonary system is therefore transient, developmentally regulated, and mostly located in vascular structures. By these three characteristics, its expression contrasts with that of AT1A, which is continuously expressed in the cardiac muscle to adulthood. This spatiotemporal pattern of expression of angiotensin II receptor mRNAs during development suggests a possible role for angiotensin II in organogenesis.

Sex Difference in Vascular Injury and the Vasoprotective Effect of Valsartan Are Related to Differential AT 2 Receptor Expression

“…1,2 The AT 2 receptor is abundantly and widely expressed in fetal tissues, but its expression declines rapidly after birth. 3,4 Interestingly, the AT 2 receptor is reexpressed in certain pathological conditions such as inflammation and vascular injury. 1,2 These findings suggest that the AT 2 receptor plays an important role not only in vasculogenesis but also in vascular remodeling.…”

Specific single chain variable fragment (ScFv) antibodies to angiotensin II AT2 receptor: evaluation of the angiotensin II receptor expression in normal and tumor-bearing mouse lung

“…In a previous in situ hybridization study analysis in rats showed that AT 2 mRNA was detected in bronchi and trachea but very little in stroma in the E19 fetal and new born pups, whereas the expression levels of AT 2 mRNA in the adult rat lung is very low or negligible (Shanmugam et al 1996). In adult human lung tissues, AT 2 protein expression was detected in brush borders of bronchial epithelium by immunohistochemical analysis with anti-rabbit anti-AT 2 antiserum (Bullock et al 2001).…”

ANG II, ANG-(1-7), ALDO and AVP biphasic effects on Na+/H+ transport: the role of cellular calcium

“…AT2 receptors are highly expressed in a variety of tissues in developing embryos, but AT2 expression declines after birth [65,66]. Until now, the range of AT2-dependent functions and AT2-linked intracellular signaling events are still not completely understood [67].…”