Replacement of K+ with Rb+ or Cs+, and its effects on the mechanical responses to norepinephrine and methacholine in the rat vas deferens.
The rat vas deferens was stored overnight in cold, K+-free Krebs solution to deplete intracellular K+ then incubated in K+-, Rb+-, or Cs+-containing Krebs solution at 37 degrees C to load these ions inside the cells. After 4 h, the contents of K+ or Rb+ reached the level of K+ in the fresh vas deferens; the content of Cs+ was less than half that of the fresh vas deferens. Dose-response curves to norepinephrine and methacholine were determined under these conditions, and the curves in Rb+ or Cs+ solution were compared with those in K+ solution. The cold storage per se had little effect on the dose-response curves in K+ solution except that it slightly decreased the maximal response to norepinephrine. The dose-response curves in Rb+ solution were to the left of those in K+ solution. The maximal response to methacholine was greatly increased. On the other hand, the dose-response curves in Cs+ solution were to the right of those in K+ solution. The maximal responses were greatly decreased with both drugs. The results suggest that Rb+ but not Cs+ can fully substitute for K+ in the rat vas deferens response to norepinephrine and methacholine.
D000818:Animals; D001692:Biological Transport; D002118:Calcium / Q000378:metabolism; D002463:Cell Membrane Permeability; D002586:Cesium / Q000378:metabolism / Q000494:pharmacology*; D003080:Cold Temperature; D004305:Dose-Response Relationship, Drug; D066298:In Vitro Techniques; D008297:Male; D008688:Methacholine Compounds / Q000494:pharmacology*; D009130:Muscle, Smooth / Q000187:drug effects* / Q000378:metabolism; D009638:Norepinephrine / Q000494:pharmacology*; D011188:Potassium / Q000378:metabolism / Q000502:physiology*; D051381:Rats; D012413:Rubidium / Q000378:metabolism / Q000494:pharmacology*; D012964:Sodium / Q000378:metabolism; D014649:Vas Deferens / Q000187:drug effects
D008688:Methacholine Compounds; D002586:Cesium; D012964:Sodium; D012413:Rubidium; D011188:Potassium; D002118:Calcium; D009638:Norepinephrine