EXPRESSION OF AT2 RECEPTORS IN RAT FETAL SUBDERMAL CELLS

Using an in situ receptor binding assay with emulsion autoradiography, angiotensin II receptors have been localized to the subdermal/subcutaneous region of the E19 rat skin. Radioligand binding studies on membranes of epidermis, dermis, and subdermal tissues confirmed the localization of receptors to these regions and displacement of binding by PD123177 showed the receptor was AT2. Scatchard analysis of whole skin membrane binding studies showed the receptor had a K(d) Of 0.8 nM, with a B(max) of 2240 fM/mg protein. Fetal mesenchymal cells were placed in culture and angiotensin II binding which was minimal at 48 h increased by 30-50-fold after 96 h in culture with the majority of the receptors being AT2. Increasing concentrations of FBS caused a decrease in angiotensin II binding, while maintaining the same percentage of AT2 binding sites. Increasing the initial cell density at which the cells were plated dramatically increased the angiotensin II radioligand bound, while decreasing the percentage bound to AT2 receptors. These findings demonstrate the presence of both angiotensin II receptor subtypes in cultured skin mesenchymal cells. They also demonstrate that the culture conditions used can either modulate the expression of receptor subtypes or select for cells expressing a receptor phenotype. The lower number of AT2 binding sites in rapidly dividing cell cultures suggests that the AT2 receptor may not have a function in cell replication or growth.