Mittag T W, Tormay A, Severin C, Taniguchi T, Lee P Y, Wang R F, Podos S M
Department of Ophthalmology, Mount Sinai School of Medicine CUNY, New York 10029.
Invest Ophthalmol Vis Sci. 1993 Mar;34(3):606-12.
The activity of Al3+, Ga3+, and Be2+ ions in the presence of NaF to directly activate G-proteins was investigated by their potentiative effect on forskolin (FSK)-activated adenylyl cyclase in rabbit ciliary process membranes and their effects on aqueous humor dynamics in vivo.
Adenylyl cyclase (AC) was determined by radiometric conversion of ATP to cAMP by the particulate fraction of rabbit ciliary processes. Intravitreal injections of sterile solutions of analytical grade salts were made into the center of the vitreous in a volume of 20 microliters. Intraocular pressure, aqueous humor flow, and uveoscleral outflow measurements were made by pneumatonometry, fluorophotometry, and fluorescein-dextran method, respectively. Outflow facility was determined by tonography in the intact eyes and by two-level constant pressure perfusion in cannulated eyes.
Both Al3+ (EC50, 40 mumol/l) and Be2+ (EC50, 11 mumol/l) in the presence of 0.5-2 mM NaF activated the stimulatory G-protein Gs. Ga3+ was ineffective and did not antagonize the activation by Al3+. Intravitreal injections of Al3+ (1 mumol/eye) or Be2+ (0.5 or 1 mumol/eye) had no significant intraocular pressure (IOP) effect, nor did 1.5 or 3 mumol/eye of NaF, but when either cation was injected together with NaF, IOP decreased by up to 40% for up to 140 hr. At the time of maximum IOP effect (72 hr) aqueous humor flow determined by fluorophotometry was decreased in BeCl2+ NaF-treated eyes by 40% relative to BeCl2-treated eyes; however, tonographic facility of outflow was unaffected. Uveoscleral flow was also decreased by 38% in BeCl2+ NaF treated eyes.
These findings support the hypothesis that Gs activation of ciliary process adenylyl cyclase decreases aqueous humor formation rate in rabbit eyes, and that activation of G-proteins mediates contraction of ciliary muscles causing a decrease of aqueous humor outflow via the uveoscleral route. The results suggest that G-proteins putatively involved in trabecular facility changes are less sensitive to activation by BeF3- than are other parameters of aqueous humor dynamics.
通过Al3 +、Ga3 +和Be2 +离子在NaF存在下对兔睫状体过程膜中福斯高林（FSK）激活的腺苷酸环化酶的增强作用及其对体内房水动力学的影响，研究它们直接激活G蛋白的活性。
通过兔睫状体颗粒部分将ATP辐射转化为cAMP来测定腺苷酸环化酶（AC）。将分析级盐的无菌溶液以20微升的体积玻璃体内注射到玻璃体中心。分别通过眼压测量法、荧光光度法和荧光素 - 葡聚糖法测量眼压、房水流量和葡萄膜巩膜流出量。通过完整眼睛的眼压描记法和插管眼睛的两级恒压灌注法测定流出系数。
在0.5 - 2 mM NaF存在下，Al3 +（EC50，40 μmol / l）和Be2 +（EC50，11 μmol / l）均激活刺激性G蛋白Gs。Ga3 +无效且不拮抗Al3 +的激活作用。玻璃体内注射Al3 +（1 μmol /眼）或Be2 +（0.5或1 μmol /眼）对眼压（IOP）无显著影响，1.5或3 μmol /眼的NaF也无影响，但当任何一种阳离子与NaF一起注射时，眼压可降低高达40%，持续长达140小时。在最大眼压效应时（72小时），通过荧光光度法测定，BeCl2 + NaF处理的眼睛房水流量相对于BeCl2处理的眼睛降低了40%；然而，眼压描记流出系数未受影响。BeCl2 + NaF处理的眼睛葡萄膜巩膜流量也降低了38%。
这些发现支持以下假设：睫状体过程腺苷酸环化酶的Gs激活降低兔眼房水生成率，并且G蛋白的激活介导睫状肌收缩，导致房水通过葡萄膜巩膜途径流出减少。结果表明，推测参与小梁系数变化的G蛋白对BeF3 - 激活的敏感性低于房水动力学的其他参数。
