Abstract
The acetylcholine-evoked relaxation of rabbit isolated thoracic aorta precontracted by phenylephrine was studied. Phenylephrine
caused a steady contraction that was maintained for 6 h. In the presence of calcium disodium ethylenediaminetetraacetate (EDTA) and
ascorbic acid the contraction decreased with time. NG-Nitro-L-arginine abolished the inhibitory effect of EDTA and ascorbic acid. Acetylcholine evoked a rapid concentration-dependent relaxation that recovered spontaneously and slowly, but fully, with time. Relaxationevoked by equieffective concentrations of carbachol and acetylcholine had the same time course. Cumulative addition of acetylcholine (10-7- 3 x 10-5 M) caused a marked relaxation that was reverted slightly at high concentrations. The relaxation was the same with rings derived from the upper, middle, and lower part of the thoracic aorta. Two consecutive concentration-response curves for acetylch-oline obtained at a 2-h interval demonstrated a slight development of tachyphylaxis. The relaxation was inversely related to precontractile tension evoked by phenylephrine when expressed as a percentage, but independent when expressed as g tension. Storage of aorta in cold saltsolution for 24 h did not alter the relaxation. EDTA and ascorbic acid did not alter the relaxation. It is concluded that (1) EDTA and ascorbic acid can not be used with impunity to stabilize catecholamines used as preconstriction agents; (2) the reversal of the acetylcholine-evoked relaxation is not due to hydrolysis of acetylcholine; (3) the relaxation is uniform in all segments of thoracic aorta; (4) cold
storage of aorta does not alter the relaxation; and (5) acetylcholine releases the same amount of relaxing factor, irrespective of the precontractile tension.
caused a steady contraction that was maintained for 6 h. In the presence of calcium disodium ethylenediaminetetraacetate (EDTA) and
ascorbic acid the contraction decreased with time. NG-Nitro-L-arginine abolished the inhibitory effect of EDTA and ascorbic acid. Acetylcholine evoked a rapid concentration-dependent relaxation that recovered spontaneously and slowly, but fully, with time. Relaxationevoked by equieffective concentrations of carbachol and acetylcholine had the same time course. Cumulative addition of acetylcholine (10-7- 3 x 10-5 M) caused a marked relaxation that was reverted slightly at high concentrations. The relaxation was the same with rings derived from the upper, middle, and lower part of the thoracic aorta. Two consecutive concentration-response curves for acetylch-oline obtained at a 2-h interval demonstrated a slight development of tachyphylaxis. The relaxation was inversely related to precontractile tension evoked by phenylephrine when expressed as a percentage, but independent when expressed as g tension. Storage of aorta in cold saltsolution for 24 h did not alter the relaxation. EDTA and ascorbic acid did not alter the relaxation. It is concluded that (1) EDTA and ascorbic acid can not be used with impunity to stabilize catecholamines used as preconstriction agents; (2) the reversal of the acetylcholine-evoked relaxation is not due to hydrolysis of acetylcholine; (3) the relaxation is uniform in all segments of thoracic aorta; (4) cold
storage of aorta does not alter the relaxation; and (5) acetylcholine releases the same amount of relaxing factor, irrespective of the precontractile tension.
| Originalsprog | Engelsk |
|---|---|
| Artikelnummer | https://doi.org/10.1016/S1056-8719(99)00035-0 |
| Tidsskrift | Journal of Pharmacological and Toxicological Methods |
| Vol/bind | 41 |
| Sider (fra-til) | 153-159 |
| Antal sider | 7 |
| ISSN | 1056-8719 |
| Status | Udgivet - aug. 1999 |
Emneord
- Kliniske undersøgelsesmetoder, laboratorieteknologi og radiografi
- Rabbit aorta
- acetylcholine
- endothelium
- vasodilatation