Water deprivation upregulates ANG II AT(1) binding and mRNA in rat subfornical organ and anterior pituitary

We studied angiotensin Il (ANG II) receptor subtype expression in selected brain nuclei and pituitary gland after water deprivation by in vitro receptor autoradiography using I-125-labeled [Sar(1)]ANG II and by in situ hybridization using S-35-labeled AT(1A), AT(1B), and AT(2) receptor-specific riboprobes. In control rats we found binding to AT(1) receptors in the subfornical organ, paraventricular nucleus. median eminence, and anterior pituitary; AT(1A) mRNA expression in the subfornical organ and paraventricular nucleus; and AT(1B) mRNA expression in the anterior pituitary. No receptor mRNA was found in the median eminence. AT(1) receptors and AT(1A) receptor mRNA levels were increased in the subfornical organ, and, in the anterior pituitary, AT(1) receptors and AT(1B) receptor mRNA were increased, only after 5 days of water deprivation. No significant changes occurred after 1 or 3 days of water deprivation, and no regulation of ANG II receptor expression was detected in other brain areas. Our results show that prolonged water deprivation selectively regulates AT(1) receptor expression and AT(1A) and AT(1B) receptor mRNA levels in the subfornical organ and anterior pituitary, respectively, supporting a role for these receptors during sustained dehydration.