Cooperation of ATP and norepinephrine in inducing contraction in guinea pig vas deferens is not associated with change in intracellular Ca2+ level.
Contractile responses and fura-2 fluorescence signals were simultaneously recorded in fura-2 loaded longitudinal muscle strips of guinea pig vas deferens to examine the relationship between cooperation of ATP and norepinephrine (NE) in the contractile response and intracellular Ca2+ level. ATP or NE induced a rapid or delayed contraction, respectively, with concomitant changes in fura-2 signal. Addition of both agonists potentiated the rapid, but not delayed contraction, while there was no potentiation in the fura-2 signal. In another series of experiments, NE (> or = 10 microM) contracted the muscle without further concomitant increase in Ca2+ level, indicating "Ca2+ sensitization" of the contractile apparatus. These findings suggest that cooperation of ATP and NE in inducing a rapid contraction of guinea pig vas deferens is mainly due to the "Ca2+ sensitization" effect of NE.
Fujita
A
A
Department of Veterinary Pharmacology, Osaka Prefecture University, Japan.
Takeuchi
T
T
Ishii
T
T
Nishio
H
H
Hata
F
F
D000255:Adenosine Triphosphate / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D004357:Drug Synergism; D006168:Guinea Pigs; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction; D009130:Muscle, Smooth / Q000187:drug effects* / Q000502:physiology; D009638:Norepinephrine / Q000494:pharmacology*; D014649:Vas Deferens / Q000187:drug effects
D000255:Adenosine Triphosphate; D002118:Calcium; D009638:Norepinephrine