SP-I secretion by baboon embryos in vitro.

Baboon embryos cultured to postimplantation stages have been shown to secrete the placental protein SP-I into the culture medium in quantities of up to almost 5 micrograms/day, based on a rhesus monkey standard. Twelve embryos, for which spent media samples have been assayed, have been shown to secrete this protein, with measurable quantities usually being present on day four following attachment of the zonaless embryo to the culture dish. Secretion has continued for up to 14 days, with over 26 micrograms total SP-I secretion from one embryo. These observations further enhance the utility of the baboon embryo culture system as a model for studying early placental development in the primate.