The sensitivity of adrenergic varicosities to the 3H-noradrenaline-releasing effect of potassium.
After the loading of incubated, homogeneously innervated tissues with 3H-noradrenaline (monoamine oxidase and catechol-O-methyl transferase inhibited, calcium-containing solution) high K+ released the 3H-amine from adrenergic varicosities. In paired experiments the sensitivity of rat atria to high K+ exceeded that of vasa deferentia. In the rat vas deferens the releasing effect of high K+ was enhanced by drugs or procedures which induce a carrier-mediated outward transport of 3H-noradrenaline, i.e., by ouabain, by glucose deprivation and by hypoxia. In the presence of extracellular calcium desipramine failed to affect the releasing effect of high K+ (except in the absence of glucose or during hypoxia), but in the absence of calcium desipramine reduced it. Apparently, whenever the axoplasmic levels of 3H-noradrenaline are increased, high K+ is able to induce some carrier-mediated outward transport of the 3H-amine. It is suggested that "organ differences" with respect to the sensitivity to high K+ may well be due to hypoxia (plus some lack of glucose) of those varicosities that had been loaded with 3H-noradrenaline. The risk of storage of 3H-noradrenaline in hypoxic varicosities appears to be greater in incubated than in perfused organs, and in the former it is greater in sparsely than in densely innervated tissues.
Schönfeld
C L
CL
Institut für Pharmakologie und Toxikologie, Universität Würzburg, Federal Republic of Germany.
Trendelenburg
U
U
D000818:Animals; D002118:Calcium / Q000494:pharmacology; D004837:Epinephrine / Q000378:metabolism*; D006325:Heart Atria / Q000187:drug effects / Q000378:metabolism; D008297:Male; D009638:Norepinephrine / Q000378:metabolism* / Q000494:pharmacology; D010042:Ouabain / Q000494:pharmacology; D010293:Pargyline; D011188:Potassium / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D014649:Vas Deferens / Q000187:drug effects / Q000378:metabolism
D010042:Ouabain; D010293:Pargyline; D011188:Potassium; D002118:Calcium; D009638:Norepinephrine; D004837:Epinephrine