Altered in vitro uptake of norepinephrine by cardiovascular tissues of spontaneously hypertensive rats. Part 1. Mesenteric artery.

The incorporation of tritiated norepinephrine (NE) by mesenteric arteries from spontaneously hypertensive rats (SHR) of the Okamoto strain and from age-matched Wistar Kyoto (WKY) controls was studied. The arteries were incubated with tritiated NE, and fractions were isolated by differential and sucrose density gradient centrifugations. The amount of radioactivity present in certain subfractions (P3 pellet) of the SHR arteries was significantly higher than that of WKY arteries. When the P3 subfraction was lysed and subjected to sucrose density gradient centrifugation, the tritiated NE was found to ba associated with the 0.4-0.5 M interface. Electron micrographs of the P3 subfractions revealed a variety of vesicular structures which might represent storage sites for the tritiated NE. Although a number of factors could account for the finding of enhanced incorporation into mesenteric artery subfractions of hypertensive rats, the finding is compatible with the work of others who found increased ATPase activity in mesenteric arteries of SHRs, since ATPase is known to activate vesicular NE uptake.