Hormonal Influence on Lipid-Protein Interactions in Biological Membranes

It is known that prolactin modifies the fluidity of different biological membranes in rats and that the activity of intestinal alkaline phosphatase varies directly with the fluidity of the membranes in which it is found. Our objective was to study the intestinal alkaline phosphatase (IAP) activity, lipid composition and fluidity of the proximal small intestine brush border membranes under the influence of physiological high levels of prolactin, in rats with 15 days of lactating (Dams 15 days) compared with control virgin rats. The phenomenon was corroborated in dams from which the suckling pups had been withdrawn on the tenth day of lactation (Dams 10 days). The results showed a decrease on the IAP activity in dams in lactation with relation to control virgin and dams with withdrawal of pups. We found decreases in total phospholipids contents and fluidity and an increase in the micro-viscosity lipid membrane in dams with 15 days of lactating compared to virgins. In the same groups there were no differences in total lipids content and no modifications were observed in the quantity of total cholesterol and proteins. These results suggest that the changes produced by lactation could be one of the causes of alteration of brush border membranes properties by modifying the lipid-protein interactions and the alkaline phosphatase activity in the proximal small intestine.

Key words

Lactation - Alkaline Phosphatase - Rat Intestine - Brush-Burder Membranes - Lipid Composition - Membrane Fluidity - Fluorescence Polarization