Recovery of Rod Photoresponses in ABCR-Deficient Mice

Abstract

By comparison with control animals, abcr-/- mice exhibit faster rod recovery after a bleach of approximately 0.03. The data suggest that ABCR in normal rods may directly or indirectly prolong all-trans retinal clearance from the disc lumen over a significant bleaching range, and that the essential function of ABCR may be to promote the clearance of residual amounts of all-trans retinal that remain in the discs long after bleaching.

The ATP-Binding Cassette Transporter ABCA4: Structural and Functional Properties and Role in Retinal Disease

“…The initial study also suggested that delayed dark adaptation, another symptom of Stargardt disease, was present in Abca4 −/− mice, and that it was initiated by delayed clearance of all- trans -retinal, which is known to re-associate with opsin and trigger the phototrans-duction cascade (Weng et al 1999). In contrast, others have demonstrated that these animals adapt to the dark even faster than the wild-type mice (Pawar et al 2008). Likewise, the rates all- trans -retinal clearance in Abca4 −/− and wild-type mice were found comparable by other investigators (Maeda et al 2008).…”

The bisretinoids of retinal pigment epithelium

“…These findings are significant since in the Abca4 −/− mouse, a model in which bisretinoid forms in abundance, the level of PE in the outer segment membrane is reported to be increased (Weng et al, 1999). Pepperberg and colleagues have suggested that the higher level of PE in Abca4 −/− mice may facilitate sequestering of all- trans -retinal as NRPE, thereby accelerating recovery of the rod photoresponse after a 30–40% bleach (Pawar et al, 2008). …”

Fundus Autofluorescence in theAbca4−/−Mouse Model of Stargardt Disease—Correlation With Accumulation of A2E, Retinal Function, and Histology

“…This suggests that an inhibitory effect of A2E on RPE65 may not be an important contributor to delayed dark adaptation in vivo. It should be noted that protocols, background strains, assessed parameters, and analysis to describe the dark adaptation characteristics in Abca4 À/À mice vary considerably in the literature, 12,[33][34][35][36] which may be the reason heterogeneous and partly unreproducible results across studies. Our protocol assessing recovery of scotopic single flash amplitudes aimed at identifying differences in retinoid cycle kinetics after a photobleach.…”