Differential effects of calcium removal on acetylcholine- and potassium-induced contractions of rat ileal smooth muscle.
The contractile responses to 10(-6)M acetylcholine (Ach) and 100 mM K+ solution have been studied in the rat ileal smooth muscle exposed to calcium-free media (with or without 1.0 mM EGTA) to further examine the calcium pools mobilized by these agents for activation of contraction. Both stimulants produced contractions in Ca-free media, only in the absence of EGTA. The phasic component of the contractile responses to Ach as well as the tonic component of K+-induced contractions were relatively resistant to short periods of Ca-free exposure; this suggests that Ach mobilizes Ca from some tightly-bound or intracellular pool, whereas high-K+ contraction involves mobilization of Ca from some superficial or loosely-bound pool. Both Ach and high-K+ still caused phasic contractions following D600 treatment, with high-K+ stimulation also maintaining a tonic component, suggesting that in this tissue, high-K+ contractions are relatively resistant to calcium deficiency compared to Ach.
D000109:Acetylcholine / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000502:physiology*; D005711:Gallopamil / Q000494:pharmacology; D007082:Ileum / Q000187:drug effects; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects*; D011188:Potassium / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D013997:Time Factors
D005711:Gallopamil; D000109:Acetylcholine; D011188:Potassium; D002118:Calcium