Contribution of intracellular calcium to gallbladder smooth muscle contraction.
Studies were performed to evaluate the contribution of intracellular Ca2+ to gallbladder smooth muscle contraction under acetylcholine (ACh) or potassium stimulation. Gallbladder smooth muscle strips from adult guinea pigs were placed in tissue baths containing N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid (HEPES)-buffered physiological salt solution (PSS) and set to optimal length for contraction (Lo). The results were as follows, 1) A 20-min equilibration in zero Ca2(+)-0.1 mM ethylene glycol-bis( beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA) PSS virtually abolished the response to potassium but not to ACh. 2) Substitution of strontium, an inhibitor of intracellular Ca2+ release, for Ca2+ significantly decreased the contractile response to ACh (3 X 10(-5), 10(-4), and 3 X 10(-4) M). Strontium had no effect on the response to 40 and 80 mM potassium. 3) Intracellular Ca2+ depletion significantly decreased gallbladder smooth muscle contraction to ACh (10(-4) M) but had no effect on the response to potassium (80 mM). 4) Ryanodine, a compound that inhibits Ca2+ storage by the sarcoplasmic reticulum, significantly decreased the contractile response to ACh (10(-4) M) but not to potassium (80 mM). These data support the observation that the use of intracellular Ca2+ by gallbladder smooth muscle for contraction is agonist dependent.
Renzetti
L M
LM
Department of Physiology, Temple University School of Medicine, Philadelphia, Pennsylvania 19140.
Wang
M B
MB
Ryan
J P
JP
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000502:physiology*; D005704:Gallbladder / Q000187:drug effects / Q000502:physiology*; D006168:Guinea Pigs; D066298:In Vitro Techniques; D007700:Kinetics; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects / Q000502:physiology*; D011188:Potassium / Q000494:pharmacology; D013324:Strontium / Q000494:pharmacology*
D000109:Acetylcholine; D011188:Potassium; D002118:Calcium; D013324:Strontium