AJP - Endocrinology and Metabolism, Vol 250, Issue 1 18-E23, Copyright © 1986 by American Physiological Society
Potentiation of hemorrhage-evoked catecholamine release by prior blood loss in cats
D. A. Bereiter and D. S. Gann
The effect of prior blood loss on the plasma catecholamine response to
acute hemorrhage (H) was assessed in alpha-chloralose-urethane anesthetized
cats. Animals sustained an initial H period of 0 (samples only), 10, or 20%
H total blood volume. Ninety minutes after reinfusion of the shed blood,
all animals sustained a rapid 20% H. The catecholamine and arterial
pressure responses to this second 20% H were assessed every 2 min for
20-min duration. Plasma norepinephrine increased modestly in the 0/20%
group (+0.63 +/- 0.13 ng/ml) and 10/20% group (+0.66 +/- 0.07 ng/ml),
whereas the 20/20% group showed a much larger (P less than 0.01) mean
increase of 3.58 +/- 1.16 ng/ml. Plasma epinephrine did not increase after
0/20% (+0.05 +/- 0.02 ng/ml), increased slightly after 10/20% H (+0.10 +/-
0.05 ng/ml), and demonstrated a large significant increase after 20/20% H
(+0.48 +/- 0.18 ng/ml). The differential effect of 20% H on catecholamine
release, depending on the magnitude of prior blood loss, was not the result
of altered mean arterial or pulse pressure responses to H. Correlation
analyses revealed that the mean increases in epinephrine and norepinephrine
during the post-H sampling period were well correlated in each animal (r =
0.864, P less than 0.001). The data indicate that the priming effect of
prior blood loss on H evoked catecholamine release: requires an initial
blood loss of 20% of total blood volume; occurs rapidly, as it is seen by
90 min after the initial H period; and affects epinephrine and
norepinephrine similarly. We conclude that the immediate past secretory
history of the sympathoadrenal system affects its responsiveness to
subsequent blood loss.
