Lipid synthesis in vitro by rabbit Meibomian gland tissue and its inhibition by tetracycline.

Rabbit Meibomian gland tissue was incubated with radioactive acetate, propionate, valine, leucine or isoleucine. The time-course of incorporation of radioactivity into total lipids from acetate and isoleucine was studied in Hanks' or Krebs medium. Incorporation of acetate or isoleucine into lipid classes was followed by TLC, and of acetate label into individual fatty acids and alcohols by GLC with radioactivity detection. Radioactivity was highest in the minor acid components C16:1 and C18:1. Levels in branched fatty acids fell with chain length, reflecting the time-course of successive chain elongations. Use of amino acids or propionate as precursors suggested that molecules containing a specific branched structure were preferentially incorporated; this indicates a binding preference at the level of the fatty acid synthase which might explain the very high proportion of anteiso-branched structures in the rabbit secretion. Incorporation of label into total lipids was significantly reduced by tetracycline in the medium, with 50% reduction at about 1.5 mg/ml for acetate and 0.7 mg/ml for isoleucine.