Prolactin is an important pituitary hormone in mammals that works with oxytocin to provide milk for offspring. It also plays a role in promoting bonding between new mothers and their offspring. But did you know that non-mammalian vertebrates have prolactin too? Considering non-mammalian organisms do not have mammary glands, it must serve a different purpose in these animals.
As it turns out, prolactin is very important in the ability for teleost fish like mummichogs (Fundulus heteroclitus) to live in freshwater. Researchers at Skidmore College presented their findings on how prolactin binds to receptors in the gills and intestines of mummichogs to regulate salt and water balance at the Experimental Biology conference in Philadelphia last month. This function of prolactin is what helps the animals adapt to environments with varying levels of salt. Other researchers discovered that a prolactin-like gene also plays a role in the development of the retina in zebrafish.
It is so neat how the same hormone can have such different functions in various organisms.
X Huang, MNY Hui, Y Liu, DSH Yuen, Y Zhang, WT Chan, HR Lin, SH Cheng, CHK Cheng. Discovery of a novel prolactin in non-mammalian vertebrates: Evolutionary perspectives and its involvement in teleost retina development. PLoS One. 4(7): e6163, 2009.
S Bradley, K Puterbaugh, A Hageman, A Verspyck, L Shaw, L Danielson, Y Hou, J Breves. Prolactin directs branchial and intestinal gene expression of solute transporters and aquaporins in mummichog (Fundulus heteroclitus). 2022 Experimental Biology conference abstracts.