Singh J, Flitney F W
Pflugers Arch. 1981 Nov;392(1):1-6. doi: 10.1007/BF00584573.
A study has been made of the effects of uridine 5'-triphosphate (UTP) on the isolated frog ventricle. Preparations were superfused with solutions containing different concentrations of UTP, and changes in contractility, cyclic nucleotide levels and membrane potential were measured. UTP produced a long lasting increase in isometric twitch tension, which was unaffected by adrenergic receptor antagonists (propranolol and phentolamine). The levels of adenosine 3',5'-cyclic monophosphate (cyclic AMP) and guanosine 3',5'-cyclic monophosphate (cyclic GMP) were measured at different times during exposure of the ventricle to 10(-4) M UTP. The increase in the force of contraction was found to be accompanied by a rise in intracellular cyclic AMP. Cyclic GMP levels were seen to fall initially, but then to increase later, as both twitch and cyclic AMP started to decline. UTP also produced marked changes in the shape of the action potential; its duration and positive overshoot were both increased. The effects of UTP on twitch tension, cyclic nucleotide levels and action potential parameters were all dose-related. The change in contractility was found to be linearly related to (a) the ratio of the amount of cyclic AMP: cyclic GMP present in the fibres, and (b) to the increase in duration of the action potential. These results suggest that cyclic AMP, cyclic GMP and the availability of Ca2+ may all be involved in mediating the response to UTP.
一项关于尿苷 5'-三磷酸（UTP）对离体蛙心室影响的研究已经展开。将制剂用含有不同浓度 UTP 的溶液进行灌流，并测量收缩性、环核苷酸水平和膜电位的变化。UTP 使等长收缩张力产生持久增加，这不受肾上腺素能受体拮抗剂（普萘洛尔和酚妥拉明）的影响。在心室暴露于 10⁻⁴ M UTP 的不同时间测量腺苷 3',5'-环一磷酸（环磷酸腺苷，cAMP）和鸟苷 3',5'-环一磷酸（环磷酸鸟苷，cGMP）的水平。发现收缩力的增加伴随着细胞内环磷酸腺苷的升高。随着收缩和环磷酸腺苷开始下降，环磷酸鸟苷水平最初下降，但随后上升。UTP 还使动作电位的形状产生显著变化；其持续时间和正超射均增加。UTP 对收缩张力、环核苷酸水平和动作电位参数的影响均与剂量相关。发现收缩性的变化与（a）纤维中存在的环磷酸腺苷：环磷酸鸟苷的量的比值，以及（b）动作电位持续时间的增加呈线性相关。这些结果表明，环磷酸腺苷、环磷酸鸟苷和 Ca²⁺的可用性可能都参与介导对 UTP 的反应。
