Immunohistochemical localization and characterization of distinct angiotensin II AT1 and AT2 receptor isoforms in the adrenal glands of the Sprague-Dawley rat and the desert rodent Meriones crassus

Abstract

Employing specific polyclonal anti-AT1 and anti-AT2 antibodies, AT1 and AT2 receptor expression was immunohistochemically demonstrable within adrenal tissues in Sprague-Dawley rats and the desert rodent Meriones crassus. Among adrenal cortical zones in rats, AT1 receptor labeling was evident in zona glomerulosa and zona reticularis. In contrast, AT1 receptor labeling was confined to the zona glomerulosa and the deep zona fasiculata in Meriones crassus. AT1 receptor labeling was, however, equally observed among ganglion and chromaffin cells constituting the adrenal medulla of both animal models. AT2 receptor labeling was faint in all adrenal regions in rats. However, intensity was high in the deep zona fasiculata, and medullary chromaffin and ganglion cells in Meriones crassus. Two-dimensional Western blotting, in the presence or absence of endoglycosidase-F, revealed that structurally distinct spectra of AT1 and AT2 receptor isoforms are expressed in the adrenal tissues of each animal model. These spectra were constituted by molecular isoforms with distinct patterns of charge microheterogeneity unique to each receptor type in each animal model. In both species, heterogeneity of AT1 and AT2 receptor isoforms may be attributed in part to differential post-translational glycosylation mechanisms of the receptor polypeptide backbones, which may be critical in differentially fine-tuning adrenal functions in lab-reared and desert rodents. Key words: Angiotensin II receptors, adrenal gland, desert rodents, N –linked glycosylation, immunohistochemistry.