Production and Regulation
In humans, prolactin is produced at least in the pituitary, decidua, myometrium, breast, lymphocytes, leukocytes and prostate.
Pituitary PRL is controlled by the Pit-1 transcription factor and ultimately dopamine, extrapituitary PRL is controlled by a superdistal promoter and apparently unaffected by dopamine.
In decidual cells and in lymphocytes the distal promoter and thus prolactin expression is stimulated by cAMP. Responsivness to cAMP is mediated by an imperfect cAMP–responsive element and two CAAT/enhancer binding proteins (C/EBP). Progesterone has been observed to upregulate prolactin synthesis in the endometrium but decreases it in myometrium and breast glandular tissue. However breast and other tissues may also express the Pit-1 promoter in addition to the distal promoter.
Extrapituitary production of prolactin is thought to be special to humans and primates and may serve mostly tissue specific paracrine and autocrine purposes. It has been hypothesized that in other vertebrates such as mice a similar tissue specific effect is achieved by a large family of prolactin like proteins controlled by at least 26 paralogous PRL genes not present in primates.
Read more about this topic: Prolactin
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