Angiotensin-like immunoreactive cells in the chicken retina

The cellular distribution of Angiotensin II (ANGII) in the chicken retina was studied by immunocytochemical methods. Three different antibodies directed against ANGII revealed a distinct subpopulation of ANGII-positive amacrine cells. Their cell bodies were located in the innermost rows of the inner nuclear layer (INL). ANGII-positive cell bodies also were found in the ganglion cell layer (GCL). Faint labelling in the centre of the INL was visible, probably related to Müller cell bodies. Single ANGII-positive fibres, each arising from an amacrine cell body, ran to sublayer 3 or 5 of the INL, forming narrow plexi. In addition, small fibres connecting sublayer 3 with sublayer 5 could be observed. ANGII-positive fibres could neither be detected in the optic nerve nor in the outer parts of the retina. Incubation of the tissue in ANGII or angiotensin I (ANGI) dissolved in Ringer solution prior to fixation, increased number and intensity of labelled cells and resulted in better labelling of sublayers 3 and 5 of the inner plexiform layer (IPL). Blockage of the conversion of ANGI to ANGII by adding captopril to the ANGI containing pre-incubation medium reduced the ANGII induced staining enhancement. All three ANGII-antibodies showed corresponding results. These results indicate that a subpopulation of amacrine cells contains angiotensin II in chicken retina. This subpopulation is apparently able to take up ANGII and ANGI, to convert ANGI to ANGII and to store ANGII.