Glycosylation abolishes an in vitro insulin-like action of prolactin.
Ovine prolactin stimulated 14C-CO2 production from labeled glucose in adipose tissue of hypophysectomized rats in vitro, an insulin-like activity. Glycosylation of the hormone by attachment of a carbohydrate unit at asparagine31 abolished this in vitro insulin-like action. However, neither nonglycosylated nor glycosylated prolactin exhibited in vivo insulin-like action, as they did not lower serum glucose or non-esterified fatty acids in fasted hypophysectomized rats. Hindrance of receptor binding by the carbohydrate unit may account for the absence of in vitro insulin-like activity in glycosylated prolactin, but the dichotomy between in vivo and in vitro insulin-like actions for prolactin remains obscure.
Frigeri
L G
LG
Lewis
L J
LJ
Teguh
K
K
Lewis
U J
UJ
D000273:Adipose Tissue / Q000378:metabolism; D000818:Animals; D002245:Carbon Dioxide / Q000378:metabolism; D006023:Glycoproteins / Q000494:pharmacology*; D007016:Hypophysectomy; D007328:Insulin / Q000494:pharmacology; D008297:Male; D011388:Prolactin / Q000494:pharmacology*; D011499:Protein Processing, Post-Translational; D051381:Rats; D013329:Structure-Activity Relationship
D006023:Glycoproteins; D007328:Insulin; D002245:Carbon Dioxide; D011388:Prolactin