Effects of enprofylline, theophylline and terbutaline on second inward currents in papillary muscles from ferrets and guinea-pigs.
In ferret and guinea pig papillary muscles enprofylline (10 microM-10 mM) and theophylline (0.1-2 mM) alone or in combination with terbutaline (0.05 microM-0.1 microM) decreased the action potential duration and increased the plateau height, increased the peak force of contraction and facilitated the depolarization-induced automaticity. In voltage clamp, the xanthines alone or in combination with terbutaline increased second inward currents, ICa,f and ICa,2, but had relatively less effect on the time-dependent outward current. No qualitative differences between enprofylline and theophylline could be detected but the former was about 5 times more potent in increasing ICa,f. In clinically relevant concentrations, enprofylline and theophylline alone, or in combination with terbutaline caused a small (2-5%) shortening of the action potential.
Arlock
P
P
Department of Zoophysiology, University of Lund, Sweden.
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D001993:Bronchodilator Agents / Q000494:pharmacology*; D005260:Female; D005289:Ferrets; D006168:Guinea Pigs; D066298:In Vitro Techniques; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects; D010210:Papillary Muscles / Q000187:drug effects* / Q000502:physiology; D013726:Terbutaline / Q000494:pharmacology*; D013806:Theophylline / Q000494:pharmacology*; D014970:Xanthines / Q000494:pharmacology*
D001993:Bronchodilator Agents; D014970:Xanthines; D013806:Theophylline; C034347:enprofylline; D013726:Terbutaline