Altered in vitro uptake of norepinephrine by cardiovascular tissues of spontaneously hypertensive rats. Part 2. Portal-mesenteric veins and atria.

Norepinephrine (NE) incorporation by portal-mesenteric veins (P-M) veins) and atria of spontaneously hypertensive rats (SHR) were compared with that of age-matched Wistar Kyoto controls (WKY). Tissues were incubated in the presence of tritiated norepinephrine (3H-NE), and fractions were isolated by means by differential and sucrose density gradient centrifugation. The peak of radioactivity was located in the 0.4-0.5 M sucrose region that contained vesicular materials, as shown by electron micrography. NE incorporation (picomoles/mg tissue) into the P3 subfraction of SHR atria and P-M veins was reduced; in atria, the reduction was statistically significant. These results contrasted with the enhanced 3H-NE incorporation by SHR mesenteric artery, and point out regional differences in this process.