Somatogenic and lactogenic activity of the recombinant 22 kDa isoform of human placental growth hormone

During pregnancy, the human placenta secretes a variant of pituitary growth hormone (hGH-V) differing in sequence from the pituitary growth hormone (hGH-N) by 13 amino acids substitutions, HGH-V replaces hGH-N in the maternal bloodstream during the second half of pregnancy. HGH-V is produced in two, possibly three, isoforms: a 22 kDa form, a glycosylated 25 kDa form, and a probable 26 kDa form resulting from alternative splicing of the mRNA. Here we have studied the somatogenic and lactogenic activity of recombinant 22 kDa hGH-V isoform produced in Escherichia coli and compared it with the 22 kDa form of hGH-N. The two variants exert a similar somatogenic effect on rabbit and rat cells, but differ as regards their lactogenic activity in the rat