Effects of divalent cations and La3+ on contractility and ecto-ATPase activity in the guinea-pig urinary bladder.
1. Several cations (Ba2+, Cd2+, Co2+, Cu2+, Mn2+, Ni2+, Zn2+ and La3+, all as chloride salts, 1-1000 microM) were tested in the guinea-pig urinary bladder for their ability to: (i) modify contractile responses to electrical field stimulation (EFS), ATP, alpha,beta-methylene ATP (alpha,beta-meATP), carbachol (CCh), and KCl; (ii) affect ecto-ATPase activity. 2. Ba2+ (10-1000 microM) concentration-dependently potentiated contractile responses evoked by EFS (4-16 Hz), ATP (100 microM), alpha,beta-meATP (1 microM), CCh (0.5 microM), and KCl (30 mM). Ni2+ at concentrations of 1-100 microM also potentiated contractility of the urinary bladder, but at concentrations tested its effect was not concentration-dependent. Cu2+ at a concentration of 10 microM and Cd2+ at a concentration of 1 microM potentiated responses to all stimuli, except KCl. Ni2+ at a concentration of 1000 microM and Cd2+ at a concentration of 100 microM inhibited contractions evoked by all stimuli, and at a concentration of 1000 microM Cd2+ abolished any contractions. Responses to ATP and alpha,beta-meATP were selectively inhibited by Cu2+, Zn2+ or La3+, each at a concentration of 1 mM. 3. Cu2+, Ni2+, Zn2+ and La3+ (100-1000 microM) concentration-dependently inhibited ecto-ATPase activity in the urinary bladder smooth muscle preparations, while Ba2+ and Mn2+ were without effect, and Cd2+ and Co2+ caused significant inhibition only at a concentration of 1000 microM. 4. There was no correlation between the extent of ecto-ATPase inhibition and the effect on contractile activity of any of the cations. 5. In conclusion, the ability of some divalent cations to inhibit ecto-ATPase activity and to potentiate or inhibit contractile responses in the guinea-pig urinary bladder appear to be independent effects.
Ziganshin
A U
AU
Department of Anatomy, University College London.
Ziganshina
L E
LE
Hoyle
C H
CH
Burnstock
G
G
D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D002217:Carbachol / Q000494:pharmacology; D002413:Cations, Divalent / Q000494:pharmacology*; D002712:Chlorides / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004558:Electric Stimulation; D006168:Guinea Pigs; D007811:Lanthanum / Q000494:pharmacology*; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects*; D011189:Potassium Chloride / Q000494:pharmacology; D001743:Urinary Bladder / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism
D002413:Cations, Divalent; D002712:Chlorides; D011189:Potassium Chloride; D007811:Lanthanum; D000255:Adenosine Triphosphate; D002217:Carbachol; D000251:Adenosine Triphosphatases; C027201:ectoATPase; C002630:alpha,beta-methyleneadenosine 5'-triphosphate