MDKKRSSLKGSLLLLLLLVSDLLLCKSVASLPICPSGAVNCQVSLRELFDRAVILSHYIHNLSSEMFNEFDKRYAQGRGFVTKAINSCHTSSLSTPEDKEQAQQIHHEDLLNLILRVLRSWNDPLYHLVSEVRGMQEAPEAILSKAIEIEEQNRRLLEGMEKIVGQVQPRIKENEVYSVWSGLPSLQMADEDSRLFAFYNLLHCLRRDSHKIDNYLKLLKCRIVYDSNC Prolactin 229 PRL_HORSE PRL Prolactin acts primarily on the mammary gland by promoting lactation.