Lipid composition and in vitro biosynthetic rates of neutral lipids and phosphatidylcholine in anterior and posterior chambers of the goldfish swimbladder

1. 1. Lipid composition was compared in anterior and posterior swimbladder and also in lavages of both chambers in the goldfish. 2. 2. Anterior bladder contained more phosphatidylethanolamine and sphingomyelin than posterior chamber, but phosphatidylcholine contents were similar. 3. 3. Cholesterol formed 17% of lipids in lavage-fluid in anterior chamber and 30% in posterior chamber. Lavage phospholipid contents in four pooled samples of each chamber were below detectable limits. Thus. surface-active phospholipids do not appear to be secreted by either chamber of goldfish swimbladder. 4. 4. Uptake and incorporation of [¹⁴C]-acetate into total lipids, cholesterol and free fatty acids was greater in anterior than in posterior chamber. Rates of [³H]methylcholine incorporation into phosphatidylcholine were similar in both chambers. 5. 5. Goldfish anterior and posterior swimbladder display differences in lipid composition and metabolism which may be related to functional specializations.