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Effects of Different Types of Stimulation on Cyclic AMP Content in the Rabbit Carotid Body: Functional Significance
Author(s) -
PérezGarcía M. T.,
Almaraz L.,
González C.
Publication year - 1990
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1990.tb03137.x
Subject(s) - forskolin , chemistry , carotid body , medicine , endocrinology , incubation , stimulation , cyclase , biochemistry , biology
Cyclic AMP levels in rabbit carotid bodies incubated under control conditions, 100% O 2 ‐ or 95% O 2 /5% CO 2 ‐equilibrated medium, are close to 1 pmol/mg wet tissue (range 0.4–2.43 pmol/mg). Isobutylmethylxanthine (0.5 m M ) increases cyclic AMP levels by a factor of 14 and 8 in HEPES‐and CO 2 /CH 3 O − ‐buffered medium, respectively. Forskolin (0.5–10 μ M ) applied during 30 min increases cyclic AMP levels in a dose‐dependent manner. Incubation of carotid bodies at low O 2 tensions resulted in an elevation of cyclic AMP levels both in the absence and in the presence of isobutylmethylxanthine. In the latter conditions cyclic AMP increase was maximum at an O 2 tension of 46 mm Hg and tended to decrease at extremely low Po 2 . In isobutylmethylxanthine‐containing Ca 2+ ‐free medium, cyclic AMP increased linearly with decreasing Po 2 from 66 to 13 mm Hg; the absolute cyclic AMP levels attained in Ca 2+ ‐free medium were smaller than those observed in Ca 2+ ‐containing medium at any Po 2 . The differences between Ca 2+ ‐free and Ca 2+ ‐containing media appear to be due to the action of released neurotransmitters in the latter conditions, because dopamine and norepinephrine, which are known to be released by hypoxia in a Ca 2+ ‐dependent manner, increase cyclic AMP in the carotid body. Low pH/high Pco 2 and high [K + ] e increase cyclic AMP levels only in Ca 2+ ‐containing medium. Forskolin potentiates the release of catecholamines induced by low Po 2 . These results suggest that cyclic AMP plays an important role in the modulation of the chemoreception process.