Response of chicken ductus arteriosus to hypercarbic and normocarbic acidosis.
BACKGROUND
Changes in pH can have profound effects on vascular tone and reactivity, but their influence on the ductus arteriosus (DA) remains unknown.


OBJECTIVE
To analyzethe effects of hypercarbic and normocarbic acidosis in the reactivity of the chicken DA.


METHODS
DA rings from 19-day chicken fetuses (total incubation time, 21 days) were mounted in a wire myograph for isometric tension recording.


RESULTS
In DA rings (pulmonary side) stimulated with O(2), norepinephrine (NE), KCl, or U46619, changes from control conditions (5% CO(2), 24 mM NaHCO(3), pH 7.4) to 7.5% CO(2) (pH 7.25) or 10% CO(2) (pH 7.14) induced a concentration-dependent relaxation that reached 43.0% (SD 21.3) of the O(2)-, 28.6% (SD 23.1) of the NE-, 10.4% (SD 18.7) of the KCl-, and 6.8% (SD 12.6) of the U46619-induced contraction. Hypercarbic-acidosis-induced relaxation was impaired by the non-selective K(+) channel blocker tetraethylammonium or the BK(Ca) channel inhibitor iberiotoxin. Normocarbic acidosis (5% CO(2), 12 mM NaHCO(3), pH 7.13) induced transient relaxation of the DA, which was not affected by the presence of tetraethylammonium or iberiotoxin. Euhydric hypercarbia (10% CO(2), 48 mM NaHCO(3), pH 7.46) induced a transient contraction of the DA.


CONCLUSIONS
Our results indicate that the chicken DA is very sensitive to changes in extracellular pH, and that stimulation of BK(Ca) channels may account for the ductal-relaxing effects of hypercarbic acidosis.
Moonen
Rob M J
RM
Department of Pediatrics, School for Oncology and Developmental Biology (GROW), Maastricht University Medical Center, Maastricht, The Netherlands.
Agren
Pia
P
Cogolludo
Angel L
AL
Perez Vizcaino
Francisco
F
Villamor
Eduardo
E
D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid / Q000494:pharmacology; D000138:Acidosis / Q000188:drug therapy / Q000503:physiopathology*; D000818:Animals; D002245:Carbon Dioxide / Q000097:blood; D002642:Chick Embryo; D004373:Ductus Arteriosus / Q000187:drug effects / Q000503:physiopathology*; D006863:Hydrogen-Ion Concentration; D006935:Hypercapnia / Q000188:drug therapy / Q000503:physiopathology*; D009638:Norepinephrine / Q000494:pharmacology / Q000502:physiology; D010455:Peptides / Q000494:pharmacology / Q000502:physiology; D026902:Potassium Channel Blockers / Q000494:pharmacology; D015221:Potassium Channels / Q000494:pharmacology / Q000502:physiology; D019789:Tetraethylammonium / Q000494:pharmacology
D010455:Peptides; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D002245:Carbon Dioxide; D019789:Tetraethylammonium; D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; C064719:iberiotoxin; D009638:Norepinephrine