Membrane fluidity and lipid composition of rat small intestinal brush-border membranes during postnatal maturation

Abstract

Fluidity and lipid composition of rat small intestinal brush-border membranes (BBM) were studied during maturation in five age groups: newborns, sucklings (1–3 weeks), weaned (4–6 weeks), juveniles (8–10 weeks), and adults (12 weeks). Brush-border membrane fluidity was measured by steady-state fluourescence polarization. Fluorescent probes used were: 1,6-diphenyl-1,3,5-hexatriene, 1-(4-(trimethylammonium)phenyl)-6-phenyl-1,3,5-hexatriene, and a set of n-(9- antrhoyloxy) fatty acids. Fluorescence anisotropy measured with all fluorophores was increased in adult versus newborn rats ( P < 0.004). The weight ratio of saturated to cis- unsaturated fatty acids increased from birth to the suckling age ( P < 0.0004). The cholesterol to phospholipid molar ratio increased from birth to the weaned age ( P < 0.0001). Cholesterol to protein ratio and phospholipid to protein ratio decreased after the weaned age ( P < 0.004). The results not only describe maturational changes of brush-border membranes but also give a better understanding of the correlations between biophysical and biochemical data in biological membranes.