肾上腺素诱导牛视网膜色素上皮细胞内[Ca2+]升高及KCl偶联的液体吸收增加。

Epinephrine-induced increases in [Ca2+](in) and KCl-coupled fluid absorption in bovine RPE.

作者信息

Rymer J, Miller S S, Edelman J L

机构信息

School of Optometry, University of California-Berkeley, Berkeley, CA 94720-2020, USA.

出版信息

Invest Ophthalmol Vis Sci. 2001 Jul;42(8):1921-9.

PMID:11431462

Abstract

PURPOSE

To define the ionic basis for the apical epinephrine-induced increase of fluid absorption (J(V)) across isolated bovine RPE-choroid.

METHODS

Epinephrine-induced changes in RPE Ca2+ levels were monitored with the ratioing dye fura-2. Transepithelial potential, resistance, and unidirectional fluxes of (36)Cl, (86)Rb (K substitute), and (22)Na were simultaneously determined in paired tissues from the same eye mounted in modified Ussing flux chambers. Radioisotopes (5-7 microCi) were added to the apical bath of one tissue and the basal bath of the other, and the appearance of label in the opposite bath was measured.

RESULTS

Apical epinephrine (100 nM) transiently increased Ca2+ by 153 +/- 78 nM. This increase was inhibited by the alpha(1)-adrenoreceptor antagonist prazosin (1 microM) and blocked by CPA(5 microM), an inhibitor of endoplasmic reticulum Ca2+-adenosine triphosphatases (ATPases). Apical epinephrine (100 nM) more than doubled the net Cl absorption rate, increased net K ((86)Rb) absorption by fivefold, and tripled net fluid absorption (J(V)), as predicted by isotonic coupling between ion and fluid transport. The epinephrine-induced increases in ion and fluid transport were completely inhibited by apical bumetanide (100 microM).

CONCLUSIONS

Epinephrine increased fluid absorption across bovine RPE by activating apical membrane alpha(1)-adrenergic receptors, increasing Ca2+, and stimulating bumetanide-sensitive Na,K,2Cl uptake at the apical membrane and KCl efflux at the basolateral membrane.

摘要

目的

确定肾上腺素诱导离体牛视网膜色素上皮-脉络膜顶端液体吸收增加（J(V)）的离子基础。

方法

使用比率染料fura-2监测肾上腺素诱导的视网膜色素上皮细胞内Ca2+水平变化。在安装于改良Ussing通量室的同一只眼睛的配对组织中，同时测定跨上皮电位、电阻以及36Cl、86Rb（K替代物）和22Na的单向通量。将放射性同位素（5 - 7微居里）添加到一个组织的顶端浴液和另一个组织的基底浴液中，并测量标记物在相对浴液中的出现情况。

结果

顶端肾上腺素（100 nM）使细胞内Ca2+水平瞬时增加153±78 nM。这种增加被α(1)-肾上腺素能受体拮抗剂哌唑嗪（1 microM）抑制，并被内质网Ca2+-腺苷三磷酸酶（ATP酶）抑制剂CPA（5 microM）阻断。如离子与液体运输的等渗偶联所预测，顶端肾上腺素（100 nM）使净Cl吸收率增加了一倍多，使净K（86Rb）吸收率增加了五倍，使净液体吸收率（J(V)）增加了两倍。肾上腺素诱导的离子和液体运输增加被顶端布美他尼（100 microM）完全抑制。