Alpha-melanocyte-stimulating hormone stimulates sodium excretion in the salt gland of the duck.

Salt glands of ducks were induced to secrete sodium through the ingestion of salt water. In salt-adapted animals the administration of melanocyte-stimulating hormone (MSH) produced a rise in the sodium excreted by the salt gland, an effect which was not mimicked by adrenocorticotropin. Studies in vitro using incubations of gland slices and radioactive sodium ion showed that MSH increased sodium efflux, indicating that it acted directly upon the gland. We have previously observed that MSH has no effect on the pigmentary system of the duck. It is proposed that in the evolutionary process this hormone has acquired new target tissues in these birds.