Vasopressor hyperresponsiveness in New Zealand genetically hypertensive rats

The relationship of blood pressure (BP) to vascular hyperresponsiveness to norepinephrine (NE) in New Zealand genetically hypertensive (NZGH) rats was studied with an isolated, perfused hindquarters preparation. Four separate studies were conducted, and the findings were as follows. 1) Compared with New Zealand normotensive rats (NZNR), NZGH rats by 3 weeks of age clearly showed hyperresponsiveness, although the BP difference had not yet fully developed. 2) Bilateral renal denervation of NZGH at 3 weeks of age delayed the development of hypertension for 4 weeks, but did not lessen the vascular hyperresponsiveness. 3) In one-kidney, one clip renal hypertensive NZNR, vascular responsiveness was increased but remained less than that of age-matched NZGH. 4) In an F2 generation of NZGH-NZNR cross-bred rats, the average adult systolic BP was 163 mm Hg, similar to that of the NZGH parent strain; however, vascular responsiveness was reduced to an intermediate level, lower than that of NZGH but higher than that of NZNR. It is concluded that the vascular hyperresponsiveness of NZGH rats to NE is a primary characteristic that can be largely dissociated from elevated BP.