Role of prolactin-like protein (PRL-L) in cold-induced increase of muscle mass in chicks

- PRL-L gene expression was increased in the skeletal muscle of chicks exposed to cold.
- Increased PRL-L was concomitant with cold-induced growth of skeletal muscle.
- C2C12 cells transduced with the PRL-L gene showed higher proliferation rates.
- In vivo localization of PRL-L protein was observed outside of myofibers.

This study examined the hypothesis that a novel prolactin-like protein gene (PRL-L) is involved in cold-induced growth of skeletal muscle in chicks. Six-day-old chicks (Gallus gallus domesticus) were exposed to cold at 4 °C or kept warm at 30 °C for 24 h. Cold exposure induced significant increases in PRL-L expression that coincided with increases in the weight of the sartorius muscle, which comprises both fast- and slow-twitch fibers. Meanwhile, no induction of PRL-L mRNA was observed in the heart, liver, kidney, brain, or fat. Myoblast cells that expressed PRL-L mRNA grew faster than untransduced cells in media containing 2% serum. These results suggested that PRL-L might be involved in in controlling cold-induced muscle growth of chicks.