Abstract
The existence and extent of regulation of human placental function by maternal or fetal hormones remains undetermined. Protein phosphorylation (PP) activated by intracellular second messenger stimulation of specific protein kinases is the final event of many hormone initiated cascade systems. PP was investigated in human placental eytosol using [32]P-ATP in the presence and absence of known and postulated second messengers: c/MP, cOMP, Calcium and Polyamines. PP was assessed by SDS polyacrylanide gel electrophoresis and autoradiography and quantitated by densitometer scanning of the autoradiograpt or counting of gels cut into 1mn slices. cAMP promoted incorporation (above basal p<.01) of .58,.47,.54 and .37 pmoles [32]P/rg cytosol protein into proteins of Tr = 72000, 58000, 52000 and 45000. Half maximal phosphorylation of the major 45000 Mr protein occurred with 1.1±2×10[-7]M cAMP. cOMP activated PP of the same proteins as cAMP. However, half maximal activation required 10[-5]. cCMP and cCMP PP was inhibited by cAMP dependent protein kinase inhibitor. Calcium activated PP of 4 proteins (p<.02) (Mr=97000, 90000, 20000, and 19000). Half maximal PP occurred with 10[-7] Ca. Calmodulin and phospholipids did not change Ca activated PP. The polyamine, spermine(10[-2]M), promoted [32]P incorporation of 1.45±.02 and 0.96±.01 pmoles [32]P/mg cytosol protein into proteins of Mr=105000 and 55000.(p<.001) Half maximal = 3.7±1.2×10[-4]M spermine. Other polyamines showed the potency order spermine>>spermidine> putreseine. cAMP and Ca had no effect upon PP by the other second messengers, however, spermine inhibited both cAMP (IC50=5×10[-5]M spermine) and Ca activated PP. The presence of 3 sets of phosphoproteins specifically activated by distinct second messengers supports the hypothesis that human placental function may be partially regulated by maternal or fetal hormones.
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Moore, J. PROTEIN PHOSPHOLATION BY HORMONAL SECOND IN HUMAN PLACENTA. Pediatr Res 18 (Suppl 4), 156 (1984). https://doi.org/10.1203/00006450-198404001-00379
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DOI: https://doi.org/10.1203/00006450-198404001-00379