title: Effect of potassium on the release of [3H]noradrenaline from rabbit and human pulmonary artery.
abstract: The release of [3H]noradrenaline ( [3H]NA) from rabbit and human isolated pulmonary artery has been measured. Removal of external potassium ions enhanced both the resting and stimulated release of [3H]NA from the strips. On adding K+ to tissues which had been suspended in K+-free Krebs solution, the release of [3H]NA was reduced in both stimulated and unstimulated tissues. Selective inhibition of presynaptic alpha 2-adrenoceptors by yohimbine significantly potentiated the release of [3H]NA evoked by stimulation in K+-free solution. The presynaptic inhibitory effect of NA was much less pronounced when the release was enhanced by the removal of external K+. Since the activity of NA, K-ATPase may be affected by removing K+ or by adding it to tissue previously kept in K+-free solution, the results may indicate involvement of the sodium pump in NA release.
mesh_terms: D000818:Animals; D001692:Biological Transport; D004558:Electric Stimulation; D006801:Humans; D007700:Kinetics; D009638:Norepinephrine / Q000378:metabolism* / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology*; D011651:Pulmonary Artery / Q000187:drug effects / Q000378:metabolism*; D011817:Rabbits; D015016:Yohimbine / Q000494:pharmacology
chemical_list: D015016:Yohimbine; D011188:Potassium; D009638:Norepinephrine