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Gastrointestinal absorption of epidermal growth factor in suckling rats
Epidermal growth factor (EGF) was detected in the milk of adult lactating Sprague-Dawley female rats (38.85 ng/ml) and in the stomach (37.25 ng/g content) and plasma (32.36 ng/ml) of 13-day-old suckling offspring. Sixty-nanogram (0.12 mCi/ml) doses of 125I-EGF were administered orally to sucklings in 200 microliters of buffer for 0, 0.5, 1.0, and 3.0 h. Lung, liver kidney, brain, and blood each contained 1% or less of the administered radioactivity. Stomach wall (8%) and content (63%), intestinal wall (15%) and flushing (38%), and skin (18%) contained larger amounts reaching maxima in these three regions at 0, 0.5, and 3.0 h, respectively. Except for skin, a substantial amount of radioactivity from all tissues represented intact (6-90%) and immunoreactive (3-90%) EGF based on Sephadex G-25 chromatography and anti-EGF antibody binding, respectively. From 30 to 55% of the radioactivity from wall (gastric or small intestinal) or lumina was also capable of binding to A-431 cell surface receptors. Isoelectric points of major species found in stomach (4.2), intestine (4.1), and other tissues differed from that of administered EGF (4.5).
Epidermal growth factor (EGF) was detected in the milk of adult lactating Sprague-Dawley female rats (38.85 ng/ml) and in the stomach (37.25 ng/g content) and plasma (32.36 ng/ml) of 13-day-old suckling offspring. Sixty-nanogram (0.12 mCi/ml) doses of 125I-EGF were administered orally to sucklings in 200 microliters of buffer for 0, 0.5, 1.0, and 3.0 h. Lung, liver kidney, brain, and blood each contained 1% or less of the administered radioactivity. Stomach wall (8%) and content (63%), intestinal wall (15%) and flushing (38%), and skin (18%) contained larger amounts reaching maxima in these three regions at 0, 0.5, and 3.0 h, respectively. Except for skin, a substantial amount of radioactivity from all tissues represented intact (6-90%) and immunoreactive (3-90%) EGF based on Sephadex G-25 chromatography and anti-EGF antibody binding, respectively. From 30 to 55% of the radioactivity from wall (gastric or small intestinal) or lumina was also capable of binding to A-431 cell surface receptors. Isoelectric points of major species found in stomach (4.2), intestine (4.1), and other tissues differed from that of administered EGF (4.5).