THE PRODUCTION OF HORMONAL STEROIDS BY OVARIAN TISSUES OF THE CHINCHILLA (CHINCHILLA LANIGER)

SUMMARY The corpora lutea of pregnancy (primary CL), corpora lutea atretica (accessory CL), and the residual tissue (consisting of interstitial cells and a few follicles) were dissected from pregnant chinchilla ovaries, and incubated separately using [7α-3H]pregnenolone as substrate. Tritiated progesterone, 20α-hydroxypregn-4-en-3-one, androstenedione, testosterone and oestradiol-17β were identified as products. [7α-3H]Progesterone was the major hormone synthesized (yield 36–85%) by the three types of ovarian tissues, but the two types of luteal tissue were more efficient in the production of this compound. Androstenedione and oestradiol-17β were also synthesized by all the tissues incubated. The large amount of androstenedione produced suggested that it was the immediate oestrogen precursor. However, the occurrence of traces of 17α-hydroxyprogesterone and dehydroepiandrosterone made it impossible to conclude whether the 4- or 5-unsaturated pathway was preferred for the synthesis of oestrogens. Endogenous progesterone, 20α- and 20β-hydroxypregn-4-en-3-one, and oestradiol-17β concentrations in the plasma were also determined using gas—liquid chromatography. The major hormone was again progesterone. Since abortion occurred after ovariectomy, these hormones must have been of ovarian origin. The findings suggest that the accessory corpora lutea supplemented the primary corpora lutea in the production of hormones for the maintenance of gestation.