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SUMMARY1. Everted sacs of new-born pig intestines incubated in bicarbonate saline at 370 C, transferred bovine plasma albumin across the mucosa into fluid bathing the serosa, the amount transferred increasing as the concentration of albumin in the mucosal fluid was raised from 0 5 to 16 g/100 ml.2. The rate of albumin transfer across the foetal pig intestine showed an apparent maximum, about 400,tsg/g intestine/hr, 2 weeks before birth.The transfer at birth, about 200 ,ug/g intestine/hr, fell sharply during the next 2 days but later returned to that previously found at birth. 3. When sacs were prepared from the intestines of 1 to 7-day-old pigs part of the recovered albumin was degraded. No digestion was found when the intestines of new-born or foetal pigs were used.4. The transfer of water and sodium, but not glucose, measured across the foetal and new-born pig intestine, was consistently higher when albumin was present in the mucosal fluid: the transmural potential difference was lowered by the presence of albumin. These differences disappeared during the first 2 days of life.5. Both the total and ouabain-sensitive adenosine triphosphatase (ATPase) activities of the pig intestinal epithelium fell within 24 hr of birth. There was some increase in total ATPase activity in older pigs but the ouabain-sensitive activity remained low.6. The relation between albuimin and sodium transport, seen at a time when albumin is not being metabolized, suggests that the transfers are closely coupled. The movement of sodium into a mucosal cell down its own concentration gradient may provide energy for the translocation of albumin.

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To characterize the ontogenesis of hepatic epidermal growth factor (EGF) metabolism in normal BALB mice, we measured serum and liver concentrations of EGF and liver concentrations of pre-pro EGF mRNA. Female and male animals were studied at 1, 2, 5, 7, and 10 wk of life. After death, body weight and length were measured, and serum and liver tissues were collected for EGF determinations. Immunoreactive serum EGF (means +/- SE) increased at 7 and 10 wk and was significantly higher (P less than 0.05) in males (465 +/- 58 and 683 +/- 120 pg/ml) than females (188 +/- 52 and 295 +/- 64 pg/ml). Liver EGF concentrations were low at 1, 2, and 5 wk, significantly increasing (P less than 0.01) at 10 wk to 179 +/- 36 vs. 268 +/- 49 pg/mg protein for females and males, respectively (female and male values were significantly different, P less than 0.01). Pre-pro EGF mRNA was examined at 1, 2, 3, 5, 7 and 10 wk. EGF message increased in liver to highest values at 10 wk in both males and females. There was a high correlation between serum and liver EGF concentrations during the first 10 wk (r = 0.97 and 0.85 for males and females, respectively) and a twofold increase in liver EGF mRNA between 3 and 10 wk of postnatal life. These results suggest that liver may be an important source of circulating EGF in developing BALB mice.

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