Intestinal handling of an oral oleoyl-estrone gavage by the rat

Adult Zucker lean (Fa/?) female rats received a single 250 nmol oral gavage of H-3-labelled oleoyl-estrone in 0.2 ml of sunflower oil. After one hour, samples of arterial, portal and suprahepatic blood, and lymph were obtaine d and fractioned to determine the amount of radioactivity present in the fo rm of free estrone, acyl-estrone and hydrophilic estrone esters in the bloo d of each vessel. Lipoprotein fractions (chylomicra + VLDL, LDL, HDL and li poprotein-depleted plasma) were also analysed as well as the distribution o f absorbed H-3-estrone in the intestine, specific organs and carcass. About one third of the oleoyl-estrone dose recovered was found in the tissues, m ainly in the blood, the rest remaining relatively untouched in the intestin al content. High hypothalamic estrone uptake (compared with the rest of the brain) was observed. Data from non-radioactive estrone measurements showed a similar pattern of absorption and tissue distribution to that obtained b y 3H-estrone tracking alone. In both cases, most of the estrone present in the intestinal lumen was absorbed as intact oleoyl-estrone, but a significa nt part was absorbed as free estrone. There is a net transfer of 3H-estrone into portal blood HDL, and part of the 3H-estrone is also loaded into lymp h-carried chylomicra. A large share of free estrone is filtered by the live r, but most of the acyl-estrone absorbed passes unaltered. The oral adminis tration of oleoyl-estrone results in significant absorption of the unaltere d molecule, which is transferred to lymph-carried chylomicra and also direc tly to plasma HDLs. It may be inferred that the HDL fraction contains the p hysiological carrier of oleoyl-estrone in its role of ponderostat signal. ( C) 2001 Elsevier Science. All rights reserved.