OESTROGEN AND PROGESTERONE LEVELS IN PREGNANT RHESUS MONKEYS

Abstract

SUMMARY: Progesterone was chemically determined in the placental tissue of four rhesus monkeys (Macaca mulatta), and in the blood and placenta of a fifth monkey at the time of an elective caesarean section near term. The urine of the same animal was also collected before the operation and assayed for oestradiol-17β, oestrone and oestriol. Comparison with the reported results of similar assays in women revealed a marked difference between the two species. The concentrations of all steroids measured in the monkey were invariably lower than the corresponding human ones, the difference in placental progesterone being of the order of 30–40 times. Oestriol appears to be absent from the urine of pregnant macaques. The reason for the difference in hormone levels between pregnant women and rhesus monkeys would seem to be the lesser endocrine activity of the monkey placenta. These findings are briefly discussed and it is tentatively concluded that in the production (and probably in the metabolism) of oestrogens and progesterone during pregnancy the macaque appears more closely related to the domestic animals than to the higher primates.