Elevated plasma adrenaline in spontaneously hypertensive rats.

Having found that circulating adrenaline (AD) is selectively elevated in stroke-prone spontaneously hypertensive rats (SHRSP) compared with Wistar-Kyoto rats (WKY), we extended the comparison to include other normotensive and hypertensive rat strains. Aortic catheters were implanted in young (5-7 weeks) and old (7-9 months) WKY, Black-Hooded Wistar (BHW), Sprague Dawley (SD), spontaneously hypertensive rats (SHR) and SHRSP for repeated measurement of mean arterial pressure (MAP) and blood sampling under conscious resting conditions. In the young SHR and SHRSP, MAP was already significantly higher than in age-matched WKY but MAP in the SD rats was similar. Plasma AD was significantly higher in SHR and lower in SD rats when compared with WKY. There was no difference in plasma noradrenaline (NA) between strains at this age. At the older age, MAP was 40-60 mmHg higher in SHR and SHRSP than in WKY and BHW but was significantly lower in the SD strain. Circulating AD did not differ between the normotensive strains but was 3-4 times higher in the hypertensive strains. Plasma NA was elevated in SHR only. The acute reduction of MAP caused by ganglion blockade (an index of the sympathetically mediated component of resting blood pressure) was greater in SHR and SHRSP than in WKY at the older age only. However, the residual MAP after ganglion blockade was significantly higher in the hypertensive strains at both ages. Regression analysis showed that in the older rats, plasma AD was correlated with resting MAP, the reduction in MAP with ganglion blockade, the residual MAP and plasma NA.(ABSTRACT TRUNCATED AT 250 WORDS)