Usachev Y, Verkhratsky A
Department of General Physiology of the Nervous System, Bogomoletz Institute of Physiology, Kiev, Ukraine.
Cell Calcium. 1995 Mar;17(3):197-206. doi: 10.1016/0143-4160(95)90034-9.
The intracellular free calcium concentration ([Ca2+]i) was recorded from freshly isolated rat dorsal root ganglia (DRG) neurones by means of Fura-2 or Indo-1-based microfluorimetry. Extracellular application of IBMX at millimolar concentrations evoked transient elevations in [Ca2+]i. The amplitude and rate of rise of the [Ca2+]i transient increased with increasing IBMX concentration. The effects of IBMX on [Ca2+]i were not mimicked by direct manipulation of the intracellular level of cyclic nucleotides, nor incubation with dibutyryl-cAMP, cGMP or 8-bromo-cGMP; neither did treatment with forskolin induce similar [Ca2+]i transients. The IBMX-evoked [Ca2+]i elevation persisted in Ca(2+)-free extracellular solutions, suggesting its origination was from intracellular stores. Caffeine-induced depletion of internal Ca2+ pool prevented IBMX-evoked [Ca2+]i responses, and vice versa, IBMX treatment strongly reduced the amplitude of subsequent caffeine-induced [Ca2+]i elevation. Both ryanodine and procaine, agents known to interact with Ca(2+)-gated Ca2+ release channels of the intracellular endoplasmic reticulum calcium stores, effectively inhibited IBMX-induced [Ca2+]i transients. We suggest that, in addition to its known phosphodiesterase-inhibiting activity, IBMX is an effective liberator of Ca2+ from ryanodine/caffeine-sensitive internal calcium stores in neural cells.
采用基于Fura-2或Indo-1的显微荧光测定法，从新鲜分离的大鼠背根神经节（DRG）神经元中记录细胞内游离钙浓度（[Ca2+]i）。以毫摩尔浓度在细胞外施加异丁基甲基黄嘌呤（IBMX）可引起[Ca2+]i的短暂升高。[Ca2+]i瞬变的幅度和上升速率随IBMX浓度的增加而增加。直接操纵细胞内环核苷酸水平，或与二丁酰环磷腺苷（dibutyryl-cAMP）、环磷鸟苷（cGMP）或8-溴环磷鸟苷（8-bromo-cGMP）孵育，均不能模拟IBMX对[Ca2+]i的作用；用福斯可林处理也不会诱导类似的[Ca2+]i瞬变。在无钙的细胞外溶液中，IBMX引起的[Ca +]i升高持续存在，这表明其来源是细胞内储存库。咖啡因诱导的细胞内Ca2+池耗竭可阻止IBMX引起的[Ca2+]i反应，反之亦然，IBMX处理可强烈降低随后咖啡因诱导的[Ca2+]i升高的幅度。已知与细胞内内质网钙储存的钙门控Ca2+释放通道相互作用的药物，如ryanodine和普鲁卡因，均能有效抑制IBMX诱导的[Ca2+]i瞬变。我们认为，除了其已知的磷酸二酯酶抑制活性外，IBMX还是神经细胞中ryanodine/咖啡因敏感的细胞内钙储存中Ca2+的有效释放剂。
