The postnatal development of intestinal @entity6741 transport in the @entity35 was examined using the villus technique. Jejunal uptake of @entity7362 was linear with respect to incubation concentration at all study ages. Ileal uptake was linear with @entity7362 concentration during the first 2 postnatal weeks; a curvilinear relationship indicating the presence of saturable transport appeared during the third week. With the appearance of ileal active transport at age 3 weeks, the Km (app) was constant at 0.49 mM, 0.59 mM, and 0.50 mM in 3-week, 4-week, and adult animals, respectively. The V(app) was 14.65 nmol X mg-1 (dry wt) X min-1 at 3 weeks and declined with age to 11.40 and 10.51 nmol X mg-1 (dry wt) X min-1 in 4-week and adult animals, respectively. The role of physico-chemical changes in the microvillus membrane in the development of ileal active transport was examined. With increasing postnatal age, microvillus membrane @entity165 content rose while the phospholipid content remained unchanged in both ileum and jejunum. Corresponding rises in the @entity165 /phospholipid ratio were observed in both sites. Simultaneously, the microvillus membrane @entity844 composition was changing from predominantly saturated to unsaturated species in both ileum and jejunum. The microvillus membrane fluorescence anisotropy (r) increased with postnatal age in jejunum when measured at 25 degrees C and 37 degrees C and ileum when measured at 25 degrees C; however, no change was noted in ileum when measured at 37 degrees C. Ileal active @entity6741 transport develops during the third postnatal week, and is associated with concurrent changes in membrane lipid composition and fluidity when measured at 25 degrees C.(ABSTRACT TRUNCATED AT 250 WORDS)

Postnatal development of intestinal XXXX transport. Relationship to membrane physico-chemical changes.

@entity7362 :: ('MESH:D013656', 'Chemical') :: ['taurocholate'] @entity844 :: ('CHEBI:35366', 'Chemical') :: ['fatty acid'] @entity6741 :: ('CHEBI:3098', 'Chemical') :: ['bile salt'] @entity35 :: ('10116', 'Species') :: ['rat'] @entity165 :: ('MESH:D002784', 'Chemical') :: ['cholesterol']
@entity6741 :: (CHEBI:3098,Chemical) :: ['bile salt']
