The maturational changes in the degree of homologous passive cutaneous anaphylaxis (PCA) and the histamine release from peritoneal mast cells induced by several secretagogues were studied using Wistar rats (4-40 weeks old). Although the increase in vascular permeability of the rat skin induced by intradermal injection of histamine did not change significantly from one maturation period to the next, 6- to 8-weeks old rats were both the most susceptible to PCA reactions and the most responsive to histamine-releasing stimuli. Among rats in this age group (6-8 weeks), the fluidity of the resting cell membrane and the extent of membrane fluidity increase in response to compound 48/80 were greatest. Analysis of the lipid composition of mast cells indicated that the ratio of cholesterol to phospholipids was lowest at the age of 6-8 weeks. From the present study, we concluded that the maturational changes in the extent of histamine release seem to be related to membrane fluidity, which has a profile similar to that of maturation.
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