Watanabe K, Chiou G C
Ophthalmic Res. 1983;15(3):160-7. doi: 10.1159/000265251.
The effect of timolol on the active transport system in the iris root-ciliary body of rabbits was studied to elucidate the action mechanism of timolol. Neither Na+-K+-adenosine triphosphatase (ATPase) nor Mg++-ATPase was inhibited by timolol at 1 X 10(-4) M concentration. None of the energy production parameters (oxygen consumption, glucose metabolism, and lactic acid formation) was inhibited by timolol either. Further, the biosynthesis of prostaglandins E2 and F2 alpha was not affected by timolol at 1 X 10(-3) M. The blood flow to the eye was measured with a 85Sr-microsphere method. It was found that the blood flow in the iris root-ciliary body and choroid was significantly reduced by a topical application of 0.25% timolol. The dopamine concentration in the iris root-ciliary body was reduced by timolol at 1 X 10(-5) M concentration. Neither epinephrine nor norepinephrine concentration was altered by timolol. The results indicate that timolol reduces the rate of aqueous humor formation through reduction of blood flow to the ciliary process rather than via the inhibition of the active transport system or that of prostaglandin biosynthesis.
为阐明噻吗洛尔的作用机制，研究了噻吗洛尔对兔虹膜根部 - 睫状体中主动转运系统的影响。在1×10⁻⁴M浓度下，噻吗洛尔既不抑制钠钾 - 三磷酸腺苷酶（ATP酶），也不抑制镁离子 - ATP酶。噻吗洛尔也未抑制任何能量产生参数（耗氧量、葡萄糖代谢和乳酸形成）。此外，在1×10⁻³M浓度下，噻吗洛尔对前列腺素E2和F2α的生物合成没有影响。用⁸⁵Sr微球法测量眼部血流量。发现局部应用0.25%噻吗洛尔可使虹膜根部 - 睫状体和脉络膜的血流量显著降低。在1×10⁻⁵M浓度下，噻吗洛尔可降低虹膜根部 - 睫状体中的多巴胺浓度。噻吗洛尔既未改变肾上腺素浓度，也未改变去甲肾上腺素浓度。结果表明，噻吗洛尔通过减少睫状体的血流量而非通过抑制主动转运系统或前列腺素生物合成来降低房水生成速率。
