1996•The Japanese Journal of PharmacologyOpen access
Cooperation of ATP and Norepinephrine in Inducing Contraction in Guinea Pig Vas Deferens Is Not Associated with Change in Intracellular Ca2+ Level
Akikazu Fujita, Tadayoshi Takeuchi, Toshiaki Ishii, Hideaki Nishio, Fumiaki Hata
Open full text 8 citations
Abstract
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.