Yamaki H, Morita K, Kitayama S, Imai Y, Itadani K, Akagawa Y, Dohi T
Department of Removable Prosthodontics, Hiroshima University School of Dentistry, Japan.
J Dent Res. 1998 Oct;77(10):1807-16. doi: 10.1177/00220345980770100801.
Cyclic ADP-ribose (cADPR), a novel putative messenger of the ryanodine receptor, was examined regarding its ability to mobilize Ca2+ from intracellular Ca2+ stores in isolated cells of parotid and submandibular glands of the dog. cADPR induced a rapid and transient Ca2+ release in the digitonin-permeabilized cells of salivary glands. cADPR-induced Ca2+ release was inhibited by ryanodine receptor antagonists ruthenium red, ryanodine, benzocaine, and imperatoxin inhibitor but not by the inositol 1,4,5-trisphosphate (IP3)-receptor antagonist heparin. Thapsigargin, at a concentration of 3 to 30 microM, inhibited IP3-induced Ca2+ release, while higher concentrations were required to inhibit cADPR-induced Ca2+ release. Cross-potentiation was observed between cADPR and ryanodine or SrCl2, suggesting that cADPR sensitizes the Ca2+-induced Ca2+ release mechanism. Cyclic AMP plays a stimulatory role on cADPR- and IP3-induced Ca2+ release in digitonin-permeabilized cells. Calmodulin also potentiated cADPR-induced Ca2+ release, but inhibited IP3-induced Ca2+ release. Acetylcholine and ryanodine caused the rise in intracellular free Ca2+ concentration ([Ca2+]i) in intact submandibular and parotid cells. Caffeine did not produce any increase in Ca2+ release or [Ca2+]i rise in any preparation. ADP-ribosyl cyclase activity was found in the centrifuged particulate fractions of the salivary glands. These results suggest that cADPR serves as an endogenous modulator of Ca2+ release from Ca2+ pools through a caffeine-insensitive ryanodine receptor channel, which are different from IP3-sensitive pools in canine salivary gland cells. This system is positively regulated by cyclic AMP and calmodulin.
环磷酸腺苷核糖（cADPR）是一种新型的、可能的ryanodine受体信使分子，研究了其从犬腮腺和颌下腺分离细胞的细胞内钙库中动员钙离子（Ca2+）的能力。cADPR在唾液腺经洋地黄皂苷通透的细胞中诱导快速且短暂的Ca2+释放。cADPR诱导的Ca2+释放受到ryanodine受体拮抗剂钌红、ryanodine、苯佐卡因和imperatoxin抑制剂的抑制，但不受肌醇1,4,5-三磷酸（IP3）受体拮抗剂肝素的抑制。毒胡萝卜素在3至30微摩尔浓度时抑制IP3诱导的Ca2+释放，而抑制cADPR诱导的Ca2+释放则需要更高的浓度。在cADPR与ryanodine或SrCl2之间观察到交叉增强作用，表明cADPR使Ca2+诱导的Ca2+释放机制敏感化。环磷酸腺苷（cAMP）对洋地黄皂苷通透细胞中cADPR和IP3诱导的Ca2+释放起刺激作用。钙调蛋白也增强cADPR诱导的Ca2+释放，但抑制IP3诱导的Ca2+释放。乙酰胆碱和ryanodine导致完整颌下腺和腮腺细胞内游离钙离子浓度（[Ca2+]i）升高。咖啡因在任何制剂中均未使Ca2+释放增加或[Ca2+]i升高。在唾液腺的离心颗粒部分发现了ADP核糖基环化酶活性。这些结果表明，cADPR作为一种内源性调节剂，通过对咖啡因不敏感的ryanodine受体通道从钙库中释放Ca2+，这与犬唾液腺细胞中对IP3敏感的钙库不同。该系统受到环磷酸腺苷和钙调蛋白的正向调节。
