Immunoreactive oxytocin synthesis in human placental tissue

The change in the amount of immunoreactive oxytocin in human term placental tissue due to cycloheximide, an inhibitory agent of protein biosynthesis, was observed by a tissue culture method. The immunoreactive oxytocin content per gram tissue was 1.81 ng/g and significantly decreased to 1.17-1.11 ng/g when the concentrations of cycloheximide were at 1-10 micrograms/ml in culture medium. The total quantity of immunoreactive oxytocin including medium content was 1.82 ng/g and significantly increased to 3.06 ng/g in the control group. However, those of the groups in which added cycloheximide was at 1-10 micrograms/ml, were 1.91-1.85 ng/g and showed no remarkable changes after incubation. The data suggest that immunoreactive placental oxytocin can be synthesized in the human placenta itself rather than in other tissues.