Radioimmunoassay of epidermal growth factor in human lenses at various stages of development of cataract

Abstract

By using a highly specific and sensitive homologous radioimmunoassay, we found that the content of epidermal growth factor (EGF) in the lateral one-third of whole cataractous human lenses (age range 45–85 yr) extracted at elective intracapsular lens surgery, varied from undetectable to 106.25 pg mg −1 water soluble protein (WSP) (mean± s.d. = 39·70±38·90). When the lenses were grouped according to the stage of the cataract, i.e. immature ( n = 3), mature ( n = 4), and hypermature ( n = 3), the means± s.d. were 92·56±26·23, 23·89±7·71, and 7·92±2·00 pg mg −1 WSP, respectively. In ten age-matched whole ‘normal’ lenses that we removed within 2–12 hr after death, the values in EGF of the lateral one-third of the lenses ranged from 2·91 to 36·40 pg mg −1 WSP (19·39±13·65). No correlation between the age of the lenses and the content of EGF could be demonstrated at the 95% confidence interval for the cataractous and ‘normal’ lenses. The quantity of endogenous EGF correlated significantly ( P < 0·01) with the clinical stage of the cataract and is probably related to the mitotic activity of the equatorial proliferative zone. We discuss the importance of EGF in normal and cataractous lenses and postulate that EGF in the lens is endogenous in origin.