Sasaki Sadao, Nakagaki Ikuko, Kondo Hisao, Hori Seiki
Department of Physiology, Hyogo College of Medicine, Nishinomiya, Hyogo 663-8501, Japan.
Pflugers Arch. 2002 Dec;445(3):342-51. doi: 10.1007/s00424-002-0965-z. Epub 2002 Nov 6.
We investigated intracellular Ca(2+) (Ca(2+)) oscillations evoked by glucagon-like peptide 1 (GLP-1) in relation to the ryanodine receptor (RyR) and Ca(2+)-induced Ca(2+)release (CICR) mechanism in pancreatic B cell HIT. GLP-1 produced Ca(2+) oscillations in the cells, both in media with and without Ca(2+), an effect inhibited by ruthenium red and mimicked by 8-Br-cAMPS. In addition, the GLP-1-evoked Ca(2+) rise was initiated at the local intercellular peripheral cytoplasm, and a resultant expansion of the intercellular space was also observed. Caffeine induced Ca(2+) elevation in the medium with or without Ca(2+), an effect inhibited by ruthenium red. GLP-1-evoked Ca(2+) oscillations were also enhanced by IBMX, and eliminated by Rp-8-Br-cAMPS or 20 microM H-89 treatments whereas they were unaffected by 2 microM H-89 treatment. Forskolin caused a transient elevation in Ca(2+) that was reduced by Rp-8-Br-cAMPS, 2 microM or 20 microM H-89. Our results indicate that GLP-1 initially generated a local Ca(2+) elevation at the peripheral cytoplasm, subsequently producing Ca(2+) oscillations that were inhibited by ruthenium red, involving ryanodine-sensitive and cAMP-activated CICR mechanisms. The cytoplasmic levels of cAMP as well as local Ca(2+) might be responsible for Ca(2+) oscillations.
我们研究了胰高血糖素样肽1（GLP-1）诱发的细胞内Ca²⁺（[Ca²⁺]i）振荡与胰腺β细胞HIT中兰尼碱受体（RyR）及Ca²⁺诱导的Ca²⁺释放（CICR）机制的关系。GLP-1在有Ca²⁺和无Ca²⁺的培养基中均可使细胞产生[Ca²⁺]i振荡，该效应被钌红抑制，且可被8-溴-cAMPS模拟。此外，GLP-1诱发的[Ca²⁺]i升高始于局部细胞外周细胞质，同时还观察到细胞间空间的扩大。咖啡因在有Ca²⁺或无Ca²⁺的培养基中均可诱导[Ca²⁺]i升高，该效应被钌红抑制。IBMX也可增强GLP-1诱发的[Ca²⁺]i振荡，而Rp-8-溴-cAMPS或20 μM H-89处理可消除该振荡，2 μM H-89处理则无此影响。福斯高林可引起[Ca²⁺]i短暂升高，Rp-8-溴-cAMPS、2 μM或20 μM H-89可使其降低。我们的结果表明，GLP-1最初在外周细胞质产生局部[Ca²⁺]i升高，随后产生被钌红抑制的[Ca²⁺]i振荡，涉及兰尼碱敏感和cAMP激活的CICR机制。cAMP的细胞质水平以及局部Ca²⁺可能是[Ca²⁺]i振荡的原因。
