Gastrointestinal absorption of epidermal growth factor in suckling rats

Abstract

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).

Enteral IGF-I enhances fetal growth and gastrointestinal development in oesophageal ligated fetal sheep

“…Since failure of clearance by swallowing is likely to apply equally to the saline and IGF-I groups in this experiment, the higher amniotic fluid levels in the IGF-I group suggests increased IGF-I concentrations in fluids entering the amniotic sac. Given the propensity of the neonatal gut to allow absorption of whole proteins (Lecce & Broughton 1973, Werhahn et al 1981, including EGF (Thornburg et al 1984, Opleta et al 1987 and IGF-I (Phillips et al 1995), it is at least theoretically possible that the infused IGF-I is absorbed by the fetal gut and excreted in the fetal urine. However, it is also possible that the infused IGF-I is acting indirectly, via an unknown second messenger of gastrointestinal origin, to increase IGF-I production in fetal oral, pulmonary or urinary secretions, placenta or membranes, and hence to increase amniotic fluid IGF-I concentrations.…”

Enteral Absorption of Erythropoietin in the Suckling Rat

“…We selected acid precipitation as a first step in these in vitro and in the in vivo degradation studies, secondary to its ease of use in localizing and determining the fate of other enteral growth factors in previous studies (7,30,31). Our initial disposition studies show that when rhEpo is present in rat milk, TCA results correlated very highly with RIA, and in vivo studies identify intact rhEpo in local gastrointestinal tissues, systemic circulation, and distant tissues.…”

Epidermal Growth Factor Binding to Neonatal Mouse Skin Explants and Membrane Preparations—Effect of Triiodothyronine

“…Recent data by Thornburg et al (27) suggests that labeled mouse EGF given orally to suckling rats undergoes molecular processing and structural alteration during absorption with subsequent accumulation of the label in skin. Although it is known that antibodies and other macromolecules are absorbed by the neonatal rat intestine during the first 18 days of life (5,6), the extent of EGF absorption is not clear.…”