Plasma progesterone and oestrogens in sheep during late pregnancy: contribution of the maternal adrenal and ovary.

Levels of progesterone were determined by competitive protein-binding techniques and oestrogens by radio-ligand binding techniques in the uterine and peripheral plasma of parturient ewes. Uterine progesterone levels began a continuous decline 4 to 5 days ante partum whereas jugular levels only declined 1 or 2 days ante partum. Peripheral plasma progesterone levels were significantly elevated in