Angiotensin II receptors in the human adrenal gland

In the present study, we have characterized distribution and pharmacological properties of angiotensin II (Ang II) receptors in human adrenals frozen immediately after removal. Autoradiographic studies indicate that Ang II receptors are present throughout the gland. Co-incubations with DUP 753, a specific antagonist of the AT1 receptor, and with PD 123319, a specific antagonist of the AT2 receptor, reveal that Ang II receptors are mainly of type 2. The AT1 receptors are detected after 16 weeks of gestation at the periphery of the gland. Competition studies and Scatchard analysis reveal a homogenous population of high affinity AT2 binding sites (Kd = 0.68 +/- 0.1 nM). Binding capacities decrease from 1080 +/- 304 fmol/mg protein at 14 weeks to 275 +/- 55 fmol/mg protein at 21 weeks. These results differ from those obtained in adult glands where autoradiographic studies reveal that the AT1 receptors are found mainly in the zona glomerulosa and AT2 receptors mainly in the medulla. These data suggest that the AT2 receptors could be involved in the morphological or functional differentiation of the human fetal adrenal gland.