The biosynthesis and metabolism of progesterone and the biosynthesis of estrogens have been studied in placental tissue from 4 species of primates (rhesus monkey, Macaque cynomolgus, squirrel monkey and baboon) in vitro. Estrone and estradiol-17β were isolated in a radiochemically homogenous form following incubation of each of the placental preparations with Δ4-androstenedione-4-14C. Using dehydro-epiandrosterone-(7α-3H or 4-14C) as substrate, rhesus monkey and baboon placental tissue yielded the same metabolites, although the extent of radioactive conversion of the substrate ot estrogens was diminished. Differences in the distribution of radioactivity between estrone and estradiol-17β and hence in the estrone/estradiol-17β ratio from the various incubations were also apparent. The formation of radioactive progesterone and 5α-pregnan-3β-ol-20-one was demonstrated in each of the placental extracts following incubation with pregnenolone-7α-3H. 20α-Dihydroprogesterone, 5α-pregnane-3β,20α-diol and 6β-hydroxyprogesterone were also isolated from extracts of incubations of baboon and rhesus monkey placental tissue. In contrast, squirrel monkey placental tissue appeared to lack 20α-hydroxysteroid dehydrogenase activity, while 6β-hydroxylase activity could not be demonstrated in placental preparations from Macaque cynomolgus. In addition, 5α-pregnane-3,20-dione was identified in extracts of incubations of rhesus monkey placental tissue. The same spectrum of metabolites was identified following incubation of placental preparations with progesterone-4-14C (except for placental preparations from Macaque cynomolgus, which were not incubated), with the addition that 5α-pregnane-3,20-dione was isolated from extracts of incubations of baboon placental tissue. In the latter incubation studies, quantitatively significant amounts of radioactivity were present as unconverted substrate at the end of the incubation period. In no case could estrogen formation be demonstrated following incubation of placental preparations with either of the C21 substrates. On the basis of these results, the endocrine activity of the primate placenta is compared to that of the human placenta and the significance of the similarities and differences between the various placentae is discussed. (Endocrinology84: 1421, 1969)
No takes yet. Share an insight, caveat, or question.
Ainsworth et al. (1969) studied this question.