Identification of a new growth hormone family protein, somatolactin-like protein, in the rainbow trout (Oncorhyncus mykiss) pituitary gland

Endocrinology. 2003 Mar;144(3):850-7. doi: 10.1210/en.2002-221005.


A cDNA encoding a new GH family protein expressed in the rainbow trout (Oncorhyncus mykiss) pituitary gland was identified. Because the deduced amino acid sequence of this cDNA shares 56% homology with rainbow trout (rt) somatolactin (rtSL), we named it as rtSL-like protein (rtSLP). Comparison of the amino acid sequences of rtGH, rainbow trout prolactin (rtPRL), and rtSLP revealed that rtSLP shares 26% and 21% identity with that of rtGH and rtPRL, respectively. Trout SLP contains not only the known GH family protein conserved domains but also all of the four cysteine residues that are responsible for the formation of two disulfide linkages in GH, PRL, and SL. Immunoblot analysis revealed that rtSLP is secreted from the pituitary gland once it is synthesized. Unlike rtSL, rtSLP mRNA was readily detectable in pituitary glands of 2-yr fish (30-34 cm in length) but not in embryos or 1-yr fish (17-25 cm in length). Furthermore, the level of rtSLP mRNA in male fish is 2-fold higher than that in female fish. These results suggest that rtSLP might play a role in regulating the reproductive maturation in rainbow trout.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Animals
  • DNA, Complementary / analysis
  • DNA, Complementary / isolation & purification
  • Fish Proteins
  • Gene Expression
  • Glycoproteins / chemistry
  • Glycoproteins / genetics*
  • Glycoproteins / metabolism
  • Molecular Sequence Data
  • Oncorhynchus mykiss / growth & development
  • Oncorhynchus mykiss / metabolism*
  • Pituitary Gland / chemistry*
  • Pituitary Gland / metabolism
  • Pituitary Hormones / chemistry
  • Pituitary Hormones / genetics*
  • Pituitary Hormones / metabolism
  • Sequence Alignment


  • DNA, Complementary
  • Fish Proteins
  • Glycoproteins
  • Pituitary Hormones
  • somatolactin protein, fish