AJP - Regulatory, Integrative and Comparative Physiology, Vol 240, Issue 1 38-R43, Copyright © 1981 by American Physiological Society
Physiological and pharmacologic effects on TH activity in rabbit and cat carotid body
C. Gonzalez, Y. Kwok, J. Gibb and S. Fidone
The carotid bodies, along with the superior cervical ganglia and the
adrenal glands, were removed from rabbits and cats and the activity of
tyrosine hydroxylase (TH), the rate-limiting enzyme in catecholamine
biosynthesis, was assayed by the method of Nagatsu (Anal. Biochem. 9:
122-126, 1964). The activities of the enzyme, in nmols tyrosine
hydroxylated x h-1 x mg tissue-1, were: carotid body, rabbit 1.29, cat
0.84; superior cervical ganglion, rabbit 8.66, cat 4.97; adrenal gland,
rabbit 0.95, cat 2.25. With respect to the carotid body, each of the
following experimental procedures resulted in a long-term increase in TH
activity in the rabbit but not in the cat: 1) severe hypoxia (5% O2 in N2
for 1 h, assay of TH 48 h later); 2) chronic transection of the carotid
sinus nerve (assay of TH at 12-15 days); or 3) administration of reserpine
(10 mg/kg at 0 and 24 h, assay of TH at 48 h). These observations are
compared with our previous findings for rat carotid body and are discussed
in relation to the role of catecholamines in chemoreception, and, in
particular, to the reported differences in dopamine action in the carotid
bodies of these different species. Our results also suggest species
differences with respect to the participation of the sympathoadrenal system
in response to reserpine and hypoxic stress.
