Increased tissue level of atrial natriuretic polypeptide in the hypothalamus and septum of spontaneously hypertensive rats

To elucidate the pathophysiological role of atrial natriuretic polypeptide (ANP) in the brain in hypertension, the tissue concentrations and contents of α-rat ANP-like immunoreactivity (α-rANP-LI) in the hypothalamus and septum of 4-week or 18-week-old spontaneously hypertensive rats (SHR) were studied using a radio-immunoassay (RIA) for α-rANP and compared with those of age-matched Wistar-Kyoto rats (WKY). The concentration and content of α-rANP-LI in these regions of both 4-week and 18-week-old SHR were significantly higher than those of WKY (P < 0.05). High performance gel permeation chromatography coupled with the RIA showed that the gel filtration profile of α-rANP-LI in SHR was essentially identical to that of WKY. Since the hypothalamus and septum are known to be critical areas for water and electrolyte balance, and blood pressure control, these results suggest that ANP plays a pathophysiological role in these brain regions of SHR.