In contrast to the classical Ang II target tissues, which contain mostly AT1 receptors, the majority of the fetal Ang II binding sites are AT2 receptors. They are located in the fetal skin, skeletal muscle, and mesenchymal cells and disappear after birth. On the basis of the location and ontogenicity of the expression of the AT2 receptors, it was suggested that they may be involved in cell differentiation and growth. Recent experiments using vascular tissue cultures showed that the AT2 receptors exert an mtiprolifera-tive effect by counteracting the AT1 receptor growth-promoting effect. Buy Asthma Inhalers Online
We found AT1 and AT2 receptors at the same locations in the fetal and maternal tissue, although in different densities. This could indicate that Ang II exerts its functions through one receptor type (AT 1) and modulates them through the other type (AT2). Further studies, however, are needed to clarify whether both receptor types are located on the same mesenchymal cells or on different cells within the same area of the fetal membranes. Non-AT1/non-AT2 Ang II binding sites were found at low densities in the bovine fetal membranes and in the placentome and the lamina propria of the endometrium. These bindings sites might also regulate growth, since Ang II was shown to stimulate proliferation of human keratinocytes in primary culture via non-AT1/non-AT2 Ang II binding sites.