Anaerobic Conversion of Acetate to Squalene by Rat Skin. ∗

Conclusions

Others have observed the stimulation produced by glucose(8), insulin(9) and electron acceptors(6,10) on lipogenesis in various tissues under oxygen. The present data show that a combination of these materials enhanced the anaerobic conversion of acetate to squalene in pieces of rat skin. The amount of activity incorporated(1620 cpm/g skin) was sufficient to serve as labeled squalene for subsequent conversions of squalene into sterol precursors or the sterols themselves.

In contrast to human skin, rat skin contains relatively little squalene(11), and most of the activity incorporated into the unsaponified fraction of rat skin under oxygen is associated with the sterols rather than with squalene. Aerobic incubation of human skin with acetate, on the other hand, yields substantial amounts of labeled squalene(5,12). Presumably, the yield of labeled squalene by human skin could be increased by an anaerobic incubation in fortified buffers like those used in the present study.

Summary. 1. Rat skin incubated anaerobically accumulated labeled squalene from acetate and only negligible amounts of labeled sterols. Incorporation of acetate into squalene was enhanced markedly by the presence of glucose in the medium. 2. Insulin, ferricyanide and methylene blue enhanced squalene synthesis in vitro in presence of glucose. Increasing amounts of insulin or ferricyanide produced regular increases in squalene synthesis until a plateau was reached; methylene blue on the other hand showed a sharp maximum at 10^-3M, with a decline at higher concentrations. 3. Skin containing labeled squalene accumulated labeled sterol on subsequent incubation under oxygen.