Processing of epidermal growth factor by suckling and adult rat intestinal cells

Preparations of intestinal villus and crypt cells were isolated from jejunal segments of suckling (14-day-old) and adult (6- to 7-wk-old) rats. These cell preparations were incubated with 125I-labeled epidermal growth factor (EGF) at 37 degrees C to determine the extent of cellular processing of 125I-EGF in vitro. 125I-EGF bound specifically to both crypt and villus cells of suckling rats and was internalized and degraded to similar extents in both cell preparations. Analysis of the 125I radioactivity in the medium and cellular extract by gel filtration on Sephadex G-25 columns demonstrated the presence of [125I]iodotyrosine (24-31%) following 30 min of incubation. This degradation of EGF was accompanied by a loss in the capacity to bind to anti-EGF antibodies (34-52%) and A431 cells (28-48%). Binding, internalization, and processing of 125I-EGF by crypt cell preparations of adult rats was similar to that of suckling rats. In contrast, little degradation of 125I-EGF to iodotyrosine and loss of cell binding capability occurred following incubation with adult villus cells. However, a considerable loss in binding to anti-EGF antibody was detected (48%). The results indicate that isolated intestinal cells are capable of degrading 125I-EGF in vitro in a manner similar to that seen after oral feeding in vivo. They also indicate differences in the processing of 125I-EGF by isolated villus cells of adult compared with suckling rat.