Kahle G, Kaulen P, Scherer V, Wollensak J
Universitäts-Augenklinik Rudolf Virchow, Berlin.
Ophthalmologe. 1993 Dec;90(6):626-30.
Chronic application of beta-blockers often induces tachyphylaxia of unknown origin. After long-term topical pretreatment of pindolol and timolol in rabbit eyes (up to 12 weeks, twice a day) beta 2-adrenergic receptors were localized and quantified with autoradiographic methods. Frozen sections of albino rabbit eyes were labelled with [125I] cyanopindolol. Quantification revealed a significant increase in the density of beta 2-receptors after premedication with pindolol in the ciliary body and the corneal epithelium. This increase was detectable after 2 weeks of premedication and reached its maximum after 4 weeks. After premedication with timolol a significant increase of beta 2-receptors in the epithelium of the ciliary body and the corneal epithelium was visible. Following pindolol over an equivalent time-course, to that of timolol administrations, an increasing number of beta 2-receptor sites was also observed. No significant changes were visible for either kind of premedication investigated (pindolol/timolol) in the corneal endothelium, the lens or the choroid. Chronic application of topically instilled beta-blocking agents leads to a significant increase in receptor density in ocular structures that are involved in aqueous humor production. This up-regulation of beta 2-adrenergic receptors might explain the intraocular events at receptor level in relation to the phenomenon of tachyphylaxis.
长期应用β受体阻滞剂常引发不明原因的快速减敏现象。在对兔眼进行品多洛尔和噻吗洛尔的长期局部预处理（长达12周，每日两次）后，采用放射自显影法对β₂肾上腺素能受体进行定位和定量分析。用[¹²⁵I]氰基吲哚洛尔标记白化兔眼的冰冻切片。定量分析显示，经品多洛尔预处理后，睫状体和角膜上皮中的β₂受体密度显著增加。这种增加在预处理2周后即可检测到，并在4周后达到最大值。经噻吗洛尔预处理后，睫状体上皮和角膜上皮中的β₂受体也显著增加。在与噻吗洛尔给药相同的时间进程内给予品多洛尔后，也观察到β₂受体位点数量增加。在所研究的两种预处理（品多洛尔/噻吗洛尔）中，角膜内皮、晶状体或脉络膜均未见明显变化。长期局部滴注β受体阻滞剂会导致参与房水生成的眼部结构中受体密度显著增加。β₂肾上腺素能受体的这种上调可能解释了与快速减敏现象相关的受体水平的眼内事件。
