Immediate effects of insulin and anti-insulins on glycolysis in spontaneous mammary tumors in mice.

Abstract

Glucolysis in spontaneous mouse mammary tumors in vitro with 0.2% glucose was inhibited 20–40% by 200 μg/cc Δ1-testololactone or 20 μg/cc testosterone (“anti-insulins”). Addition of insulin gave small but significant stimulations (8–15%) of glucolysis. Similar effects of insulin and Δ1-testololactone were obtained with fructose, but high levels of the sugar were required (2.7–5.4%.) This seems based on the greatly lowered affinity of the hexokinase for fructose. The reported effects of insulin in stimulating various anabolic functions (DNA polymerase, DNA synthesis, cell growth) require hours (4, more or less) for expression, whereas enhancement of glucolysis takes place in 5–10 minutes. The primary target for insulin in all these cases may be glucolysi.