AJP - Heart and Circulatory Physiology, Vol 266, Issue 2 435-H439, Copyright © 1994 by American Physiological Society
Plasma norepinephrine variations correlate with peripheral vascular resistance in resting humans
B. Kennedy, D. Shannahoff-Khalsa and M. G. Ziegler
Department of Medicine, University of California, San Diego Medical Center 92103.
Plasma levels of norepinephrine (NE) vary rhythmically in humans and
animals with an ultradian (shorter than 1 day) periodicity. We repeatedly
measured plasma NE levels, blood pressure, cardiac output, and total
peripheral resistance in nine normal resting subjects over 5 h. Plasma NE
correlated with total peripheral resistance (Z = 0.322, P < 0.0002) and
inversely with cardiac output (Z = -0.276, P < 0.0002) for the nine
subjects overall. The correlations were strongest in subjects with the most
spontaneous variability in total peripheral resistance. These findings
suggest that spontaneous oscillations in plasma NE levels reflect
alterations in sympathetic nervous activity to resistance blood vessels.
The negative correlation between cardiac output and plasma NE levels may
result from the very minor cardiac NE spillover into plasma and the inverse
relationship between cardiac output and total peripheral resistance.
