Halothane decreases calcium sensitivity of rat aortic smooth muscle.
OBJECTIVE
To examine the effect of halothane on the cytosolic Ca2+ concentration ([Ca2+]i)-tension relationship of rat aortic smooth muscle.


METHODS
Rat aortic rings without endothelia were loaded with the fluorescent Ca2+ indicator, Fura PE3-AM, and then mounted in organ baths. The changes in isometric tension and [Ca2+]i were measured simultaneously. In one series ionomycin (10 nM-3 microM) was added to normal Krebs' solution cumulatively in the absence and presence of halothane (1.5%, 3%). In the other series, CaCl2 (0.3-3 mM) was added to Ca2+-free Krebs' solution including high KCl (50 mM), phenylephrine (100 nM) or prostaglandin F2alpha (PGF2alpha, 1-3 microM) in the absence and presence of halothane (1.5%, 3%). The linear part of [Ca2+]i-tension relationship was analyzed by a linear regression.


RESULTS
Halothane, 1.5%, had no effect on the normal [Ca2+]i-tension relationship obtained with the calcium ionophore, ionomycin (10 nM-3 microM), but halothane 3% decreased the slope of the relationship (0.239 +/- 0.037 for control and 0.110 +/- 0.010 for halothane 3%, P < 0.05). Halothane, 1.5% and 3%, did not change the [Ca2+]i-tension relationship obtained with CaCl2 (0.3-3 mM) in the presence of high KCl (50 mM) or phenylephrine (100 nM). In contrast, halothane, 3%, inhibited the intercept of [Ca2+]i-tension relationship obtained with CaCl2 (0.3-3 mM) in the presence of prostaglandin F2alpha (PGF2alpha, 1-3 microM) (45.708 +/- 4.233 for control and 26.997 +/- 2.522 for halothane 3%, P < 0.01).


CONCLUSIONS
Halothane decreases the Ca2+ sensitivity and that in the presence of PGF2.
Kakuyama
M
M
Department of Anesthesia, Kyoto University Hospital, Japan. kakuyama@kuhp.kyoto-u.ac.jp
Nakamura
K
K
Mori
K
K
D018685:Anesthetics, Inhalation / Q000494:pharmacology*; D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects* / Q000378:metabolism; D002118:Calcium / Q000378:metabolism / Q000494:pharmacology*; D003600:Cytosol / Q000378:metabolism; D015237:Dinoprost / Q000494:pharmacology; D005456:Fluorescent Dyes; D016257:Fura-2 / Q000031:analogs & derivatives; D006221:Halothane / Q000494:pharmacology*; D066298:In Vitro Techniques; D015759:Ionomycin / Q000494:pharmacology; D007537:Isometric Contraction / Q000187:drug effects; D009119:Muscle Contraction / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects* / Q000378:metabolism; D010656:Phenylephrine / Q000494:pharmacology; D011189:Potassium Chloride / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D014662:Vasoconstrictor Agents / Q000494:pharmacology
D018685:Anesthetics, Inhalation; D005456:Fluorescent Dyes; D014662:Vasoconstrictor Agents; C098106:fura-PE3; D010656:Phenylephrine; D015759:Ionomycin; D011189:Potassium Chloride; D015237:Dinoprost; D002118:Calcium; D016257:Fura-2; D006221:Halothane