The effect of ambient temperature on papaverine-induced relaxations in canine saphenous veins.
This study was designed to measure the effect of ambient temperature (25 degrees C) on papaverine-induced relaxations in canine saphenous veins. Segments of vein were suspended in water-jacketed tissue baths at 37 degrees C, and isometric tension was recorded. After equilibration, veins were preconstricted by a median effective dose of norepinephrine 2 x 10(-6) mol/L at either 25 degrees C or 37 degrees C. Consequent dose-dependent relaxations showed that papaverine (10(-7) to 10(-3) mol/L was three times more potent as a dilator at 37 degrees C than at 25 degrees C, with half-maximal relaxations occurring at 2.2 x 10(-5) mol/L and 6.4 x 10(-5) mol/L, respectively. A 10(-4) mol/L dose of papaverine completely relaxed veins at 37 degrees C, whereas veins at 25 degrees C never fully relaxed even at ten times the standard concentration. In addition, the time for half-maximal relaxation with a 10(-4) mol/L dose of papaverine averaged 40 minutes at 25 degrees C compared with 22 minutes at 37 degrees C; this is indicative of a reduced relaxation rate at the lower temperature. These data show that papaverine is a slower and less potent dilator of canine saphenous veins at 25 degrees C than at 37 degrees C. This may have implications for the use of papaverine in the operating room, where it is usually applied at ambient temperature to reduce vasospasm of the saphenous vein during coronary artery bypass procedures.
Rusch
N J
NJ
Department of Physiology, Medical College of Wisconsin, Milwaukee.
Wooldridge
T A
TA
Olinger
G N
GN
Boerboom
L E
LE
D000818:Animals; D004285:Dogs; D004305:Dose-Response Relationship, Drug; D010208:Papaverine / Q000008:administration & dosage / Q000493:pharmacokinetics / Q000494:pharmacology*; D012501:Saphenous Vein / Q000187:drug effects*; D013696:Temperature; D013997:Time Factors; D014664:Vasodilation / Q000187:drug effects*
D010208:Papaverine