THE EFFECT OF SOME PITUITARY HORMONES ON PROGESTERONE SYNTHESIS IN VITRO BY THE LUTEINIZED OVARY OF THE COMMON OPOSSUM (DIDELPHIS MARSUPIALIS VIRGINIANA)

Summary. Luteinized ovaries of the opossum incubated in Krebs\x=req-\ Ringer bicarbonate buffer synthesized progesterone. Such synthesis could be enhanced by lh but not by fsh or prolactin. The ovaries did not incorporate acetate-1-14C into progesterone but did convert cholesterol-1,2-3H and pregnenolone-7\g=a\-3H into progesterone. lh tended to stimulate cholesterol conversion into progesterone but the effect was not significant. The thesis is advanced that, regardless of the luteotrophic or luteolytic mechanisms operating in different species, lh is steroidogenic. It is suggested that the control mechanisms for the oestrous cycle are simpler in marsupials than in other mammalian species and an understanding of the processes involved in marsupials would give a useful baseline for comparisons with other species