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° 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.