Purchase this article with an account.
JM Rymer, C Wildsoet, SS Miller; Epinephrine Decreases Cytosolic Calcium in Chick Retinal Pigment Epithelium (RPE) . Invest. Ophthalmol. Vis. Sci. 2002;43(13):719.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Purpose: Intracellular cAMP is increased by activation of beta-adrenergic receptors in chick retinal pigment epithelial cells (Koh and Chader, 1984) and by apical membrane alpha1 adrenergic receptor activation in bovine RPE (Joseph et al., 1992). In bovine RPE, cAMP activates a phospholamban-dependent decrease in basolateral membrane calcium-activated Cl conductance and net fluid absorption (Peterson et al., 1997). In chick RPE, cAMP also decreases basolateral membrane Cl conductance (Kuntz et al., 1994). In this study, we measured the effects of apically applied epinephrine on cytosolic (free) calcium (Ca) levels in chick RPE. Methods: Intact monolayers of freshly isolated chick RPE-choroid were loaded with the calcium sensitive ratiometric dye fura-2 and mounted in a modified Ussing chamber. The tissue was excited at 340 and 380 nm. The emission fluorescence was measured at ≥510 nm with a photomultiplier tube and the ratio (R) of the fluorescence intensities at 340 and 380 nm was recorded at one-second intervals. Epinephrine (500 nM) was applied to the apical surface of the tissue, and the ratio changes were recorded as a function of time. Responses were averaged from ∼50 cells in each preparation. Results: Epinephrine produced a significant decrease in the 340/380 nm ratio, indicating a decrease in cytosolic Ca. The ratio recovered to baseline following washout. In a given preparation, repeated epinephrine applications, produced ratio changes of similar time course and magnitude. Conclusion: Activation of an apical membrane adrenergic receptor in chick RPE leads to a decrease in cytosolic Ca. This result, together with previous observations in bovine (Rymer et al, 2001) and human (Quinn et al, 2001) RPE, leads to the hypothesis that epinephrine, acting via two different second messenger pathways (cAMP and Ca), can alter fluid absorption across chick RPE. Epinephrine, in concert with other paracrine signals, could increase fluid transport from retina to choroid and have a role in ocular growth regulation
This PDF is available to Subscribers Only