Evidence that depletion of internal calcium stores sensitive to noradrenaline elicits a contractile response dependent on extracellular calcium in rat aorta.
1. Noradrenaline 1 microM induced a contractile response in rat isolated aorta in the presence or in the absence of extracellular Ca2+ with depletion of intracellular Ca2+ stores. Thereafter, during incubation in the presence of Ca2+, an increase in the resting tone was observed. Such a contractile response did not occur after exposure to caffeine or 5-hydroxytryptamine. 2. This increase in tension was inhibited in a concentration-dependent manner by alpha-adrenoceptor antagonists (prazosin, phentolamine and yohimbine), the non-specific relaxing compound, papaverine and by the Ca(2+)-entry blocker, nifedipine. Therefore, this contractile process is related to depletion of Ca2+ stores sensitive to noradrenaline and is linked to Ca2+ entry through voltage-operated Ca2+ channels and alpha-adrenoceptors. 3. Phentolamine and yohimbine did not block the Ca2+ refill pathway; prazosin and nifedipine inhibited the reuptake of Ca2+ by an internal store sensitive only to noradrenaline; papaverine inhibited the refilling of caffeine- and noradrenaline-sensitive Ca(2+)-stores.
Noguera
M A
MA
Departamento de Farmacología, Facultad de Farmacia, Universidad de Valencia, Spain.
D'Ocon
M P
MP
D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000502:physiology*; D005110:Extracellular Space / Q000502:physiology*; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000502:physiology*; D009543:Nifedipine / Q000494:pharmacology; D009638:Norepinephrine / Q000494:pharmacology*; D010208:Papaverine / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D012701:Serotonin / Q000494:pharmacology
D000317:Adrenergic alpha-Antagonists; D012701:Serotonin; D002110:Caffeine; D010208:Papaverine; D009543:Nifedipine; D002118:Calcium; D009638:Norepinephrine