Feldman E L, Randolph A E
Department of Neurology, University of Michigan, Ann Arbor.
Invest Ophthalmol Vis Sci. 1993 Feb;34(2):431-7.
This study examined the effects of peptides on inositol lipid turnover and intracellular calcium (Ca2+) levels in cultured human retinal pigment epithelium (RPE).
Cultured human RPE were stimulated with bradykinin, arginine vasopressin (AVP), or bombesin. Accumulation of 3H-inositol phosphates in the presence of 10 mmol/l lithium reflected phosphoinositide (PPI) hydrolysis. Peptide-coupled changes in intracellular Ca2+ levels were determined by fura-2 fluorescence.
Bradykinin increased PPI hydrolysis to greater than 300% of basal with an EC50 of 300 nM. Bradykinin-coupled PPI turnover was linear up to 60 min and was blocked by > 90% by the B2 antagonist [Thi5,8,D-Phe7]-bradykinin. AVP stimulated PPI turnover in a linear manner by 260% with an EC50 of 800 nM. The V1 receptor antagonist [beta-mercapto-beta,beta-cyclopentamethylenepropionyl1,-O-Me-Tyr2, A rg8]- vasopressin completely inhibited AVP-induced PPI hydrolysis. Bombesin enhanced PPI hydrolysis by 185% with an EC50 of 1 nM. Stimulation was linear up to 60 min and was blocked by > 90% by the bombesin antagonist [Leu13-psi(CH2NH)-Leu14] bombesin. In fura-2-loaded human RPE cells, the resting intracellular Ca2+ concentration was 105 +/- 32 nM (n = 29). Bradykinin increased peak intracellular Ca2+ to 764 +/- 71 nM, AVP to 310 +/- 42 nM, and bombesin to 234 +/- 20.4 nM.
Peptide-stimulated inositol lipid turnover is coupled to cytosolic Ca2+ flux in cultured human RPE.
本研究检测了肽对培养的人视网膜色素上皮（RPE）中肌醇脂质周转和细胞内钙（Ca2+）水平的影响。
用缓激肽、精氨酸加压素（AVP）或蛙皮素刺激培养的人RPE。在10 mmol/l锂存在的情况下，3H-肌醇磷酸的积累反映了磷酸肌醇（PPI）的水解。通过fura-2荧光测定肽偶联的细胞内Ca2+水平变化。
缓激肽使PPI水解增加至基础水平的300%以上，EC50为300 nM。缓激肽偶联的PPI周转在60分钟内呈线性，且被B2拮抗剂[Thi5,8,D-Phe7]-缓激肽阻断>90%。AVP以线性方式刺激PPI周转达260%，EC50为800 nM。V1受体拮抗剂[β-巯基-β,β-环戊亚甲基丙酰基1,-O-Me-Tyr2, Arg8]-加压素完全抑制AVP诱导的PPI水解。蛙皮素使PPI水解增加185%，EC50为1 nM。刺激在60分钟内呈线性，且被蛙皮素拮抗剂[Leu13-psi(CH2NH)-Leu14]蛙皮素阻断>90%。在加载fura-2的人RPE细胞中，静息细胞内Ca2+浓度为105±32 nM（n = 29）。缓激肽使细胞内Ca2+峰值增加至764±71 nM，AVP使其增加至310±42 nM，蛙皮素使其增加至234±20.4 nM。
肽刺激的肌醇脂质周转与培养的人RPE中的胞质Ca2+通量相关。
