Decreased content in left atrium and increased plasma concentration of atrial natriuretic polypeptide in spontaneously hypertensive rats (SHR) and SHR stroke-prone

Abstract

The atrial contents and concentrations, and the plasma concentrations of atrial natriuretic polypeptide (ANP) in spontaneously hypertensive rats (SHR) and SHR stroke-prone (SHRSP) were measured and compared with those of agematched Wistar Kyoto rats (WKY) using a specific radioimmunoassay (RIA) for α-rat ANP (α-rANP). The contents of α-rANP-LI in the atria of SHR (19.0±0.9 μg, mean±SEM) and SHRSP (19.3±0.6 μg) were significantly lower than that of WKY (22.8±1.4 μg)(p<0.05). The atrial concentration of α-rANP-LI was also significantly lower in SHR (248.2±11.3 ng/mg, p<0.05) and tended to be lower in SHRSP (272.2±12.4 ng/mg) than that of WKY (300.0±14.2 ng/mg). Furthermore, the concentrations in the left auricles of SHR and SHRSP were significantly lower than that of WKY (p<0.01 and p<0.05, respectively). In contrast, no significant difference was observed in the α-rANP-LI concentrations in the right auricles of WKY, SHR and SHRSP. Gel filtration studies coupled with RIA showed that gel filtration profiles of the extracts from the right and left auricles of WKY, SHR and SHRSP.were essentially identical. The plasma α-rANP-LI levels in SHR (260±34 pg/ml) and SHRSP (319±19 pg/ml) were significantly higher than that in WKY (170±17 pg/ml)(p<0.05 and P<0.01, respectively). These results suggest that the secretion of ANP from the heart is increased in SHR and SHRSP compared with WKY.