APOLIPOPROTEINS IN HUMAN FETAL COLON - IMMUNOLOCALIZATION, BIOGENESIS, AND HORMONAL-REGULATION

The present investigation aimed at defining the localization of apolip oproteins (apo) A-I, A-IV, B-48, and B-100 along the crypt-villus axis of the human fetal colon, their biogenesis during gestation, and thei r hormonal regulation. Using immunofluoresence, the distribution of ap o A-I and A-IV appeared as a gradient, increasing from the developing crypt to the tip of the villus. On the other hand, apo B-100 staining was found in the crypt and the lower mid-villus region with varying in tensities in the upper villus cells, while the 2D8 antibody which reco gnizes both apo B-100 and B-48, revealed uniform staining along the cr ypt-villus axis. Apolipoprotein synthesis, determined by [S-35] methio nine labeling, immunoprecipitation, and SDS-PAGE showed a predominance of apo A-IV(53%), followed by apo A-I (23.9%), apo B-48 (13.4%), and apo B-100 [9.7%]. The synthesis of each apolipoprotein was significant ly modulated by hydrocortisone, insulin and epidermal growth factor (E CF). Apart from a decrease in apo B-100 exerted by ECF and a reduction in apo A-I resulting from the addition of insulin, the other apolipop roteins were all enhanced. Our data confirm that the fetal colon has t he capacity to synthesize apolipoprotein A-I, A-IV, B-48, and B-100 an d establish that their synthesis are modulated by hormonal and growth factors known to be involved in the regulatory mechanism of the functi onal development of human jejunum. J. Cell. Biochem. 70:354-365, 1998. (C) 1998 Wiley-Liss, Inc.