The influence of methionine-5-enkephalin on calcium uptake by the bovine aortic media.
The influence of methionine-5-enkephalin (M-5-E), an endogenous opioid receptor agonist, on calcium uptake by bovine aortic media was investigated in vitro. 45Ca was used and radioactivity was counted in a beta scintillation counter. M-5-E increases Ca2+ uptake by the preparation. This action is inhibited by naloxone and that is proof that an opioid receptor is stimulated. A comparative study showed that phenylephrine, an alpha-adrenoceptor agonist, exhibits the same action as M-5-E, whereas morphine's action is negligible. Phenylephrine contracts the deendotheliazed ring of the bovine aorta, whereas M-5-E fails to do so. It is concluded that an opioid receptor was identified at the bovine aortic smooth muscle. This receptor is stimulated by M-5-E resulting in an increase of the extracellular Ca2+ entrance. Although no relationship was observed between the receptor and the contraction mechanism, a possible role of M-5-E in the maintenance of the vascular tone cannot be excluded.
Kokkas
B
B
Department of Pharmacology, Medical Faculty, Aristotelian University, Thessaloniki, Greece.
Kotoula
M
M
Kouyoumtzis
A
A
Kouvelas
D
D
Papadopoulos
K
K
Paradelis
A G
AG
D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D002132:Calcium Radioisotopes; D002417:Cattle; D004744:Enkephalin, Methionine / Q000494:pharmacology*; D066298:In Vitro Techniques; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000378:metabolism*; D009270:Naloxone / Q000494:pharmacology; D010656:Phenylephrine / Q000494:pharmacology
D002132:Calcium Radioisotopes; D010656:Phenylephrine; D009270:Naloxone; D004744:Enkephalin, Methionine; D002118:Calcium