TRANSFORMING GROWTH-FACTOR-BETA-2 IS THE PREDOMINANT ISOFORM IN THE NEURAL RETINA, RETINAL-PIGMENT EPITHELIUM-CHOROID AND VITREOUS OF THE MONKEY EYE

Several techniques were utilized to assess the levels, disposition and cellular sources of isoforms 1 and 2 of transforming growth factor be ta (TGF-beta) in the posterior pole of the monkey eye. Freshly dissect ed tissues, as well as the saline vehicles in which dissections were p erformed, were analysed by sandwich enzyme-linked immunosorbent assay. In all tissues TGF-beta 2 was the predominant isoform, with beta 2:be ta 1 ratios of 6:1 for neural retina (as ng g(-1)) and 425:1 for vitre ous (as pmol l(-1)). Retinal pigment epithelium (RPE)-Bruch's membrane -choroid complex contained approximately 10 times the amount of both T GF-beta isoforms as neural retina. For first passage cultures of monke y RPE, TGF-beta 2, but not TGF-beta 1, accumulated over time in condit ioned media samples. Immunoreactivity for TGF-beta 2 was detected both in tissue sections of posterior pole, specifically in rod outer segme nts and RPE, and also in the first passage cultures of RPE. Antibodies to specific peptide sequences of both isoforms localized TGF-beta to the outer segments of rod photoreceptors. The apparent sequestration o f TGF-beta 2 in photoreceptor outer segments, as well as the in vitro evidence for possible synthesis and release by RPE, suggest that TGF-b eta 2 is an important modulator of visual function acting at the retin a-RPE interface.