SYNTHESIS OF HUMAN PLACENTAL LACTOGEN AND HUMAN CHORIONIC GONADOTROPIN BY POLYRIBOSOMES AND MESSENGER RNAs FROM EARLY AND FULL TERM PLACENTAS

Role of Nucleic Acids in the Regulation of Human Placental Lactogen Synthesis

“…Figure 1 shows the peak of immunoreactive nascent chains associated with polysomes having an S value which is consistent with 7-9 ribosomes per message. Using iodinated antibody, C hati-erjee et al [11] reported similar findings. Polysomes derived from term placentas appear to support the synthesis of a greater proportion of hPL than do polysomes derived from the same quantity of first trimester tissue.…”

“…The synthesis of hPL directed by placental polyribosomes in heterolog ous protein-synthesizing systems has been accomplished in several labora tories [5a, 11, 28, 56], Consistent with the current notion that endoplasmic reticulum-bound polysomes are primarily involved with the synthesis of secretable proteins, Chatterjee et al [11], H ubert and C edard [28], and V er E ecke et al [56] have reported that membrane-bound polysomes were more active in hPL synthesis than free polysomes. We recently have iden tified the size class of polysomes responsible for hPL synthesis [unpubl., 22].…”

“…To this end, hPL synthesis directed by placental RNA extracts or polysomes has been observed in heterologous cell-free systems derived from ascites tumor cells [5a], rabbit reticulocytes [28], and wheat germ [8,11,14]. In addition, hPL synthesis has recently been reported in Xenopus laevis oocytes follow ing the microinjection of placental polyribosomes [42].…”

“…Later, using radioimmunoassay, these investigators re ported that term polysomes directed the synthesis of four times as much hPL as did first trimester polysomes [5b]. Similarly, C hatterjee et al [11] found that hPL constituted 8% of proteins directed by term polysomes in a wheat germ protein-synthesizing system, whereas no hPL was detected in reaction mixtures utilizing polysomes from 10-week-old placentas. For comparison, H austrete et al [29] found about 7% of newly synthesized proteins directed by term polysomes in a wheat germ system to be hPL.…”

Immunoreactive oxytocin synthesis in human placental tissue.

“…It is well known that the human placenta synthesizes large quantities of human chorionic gonadotropin and human placental lactogen (Chatterjee et al, 1976;Boime and Buguslawski, 1974) as well as estrogen and progesterone. Oxytocic activity of placental tissue has also been reported (Cantone, 1954), but so far the biosynthesis of oxytocin by the placenta has not been demonstrated.…”