The effect of TGF alpha on intestinal solute transport.

The effect of transforming growth factor alpha (TGF alpha) and epidermal growth factor (EGF) on 3-O-methylglucose transport was examined in vitro under short-circuited conditions in stripped rabbit jejunum. Mucosal EGF, 60 ng/ml, stimulated a significant increase in net 3-O-methylglucose transport (Jnet 0.67 +/- 0.15 vs. 0.90 +/- 0.15 microEq/cm2/h; P less than 0.03; n = 6) due to an increased mucosal to serosal flux (Jms 1.2 +/- 0.2 vs. 1.5 +/- 0.2 microEq/cm2/h; P less than 0.03). In contrast, TGF alpha, when applied to both mucosal and serosal surfaces at concentrations of either 60 (n = 6) or 150 (n = 9) ng/ml had no effect on either mucosal to serosal (Jms) or net transport (Jnet) of 3-O-methylglucose. TGF alpha did induce a significant increase in the serosal to mucosal flux (Jsm 60 ng/ml 0.44 +/- 0.02 vs. 0.51 +/- 0.03, 150 ng/ml 0.55 +/- 0.03 vs. 0.64 +/- 0.05 microEq/cm2/h; P less than 0.05). When brush border surface area was examined after exposure to either 60 ng/ml TGF alpha or saline vehicle for 2 h in in vivo isolated jejunal loops no significant difference was found (control 53 +/- 1.9; n = 35 vs. TGF alpha 52 +/- 1.9 microns 2; n = 29). Bioactivity of transforming growth factor alpha was assessed by an gastric acid secretion bioassay and found to be intact. These data provide further evidence for separate and distinct functional roles for these peptides in some biological systems.