Luteal tissue slices from an African elephant in early pregnancy have been shown to synthesize progesterone from added pregnenolone. The percentage conversion (2·4%/100 mg luteal tissue/hr) is very much lower than that found for human, bovine and porcine corpora lutea. It was possible to isolate a small amount of progesterone (0·18 μg/g) from a large quantity of luteal tissue taken from another pregnant elephant; this is far below the values found in the active corpora lutea of all other mammals.
The reasons for the relative inability of elephant corpora lutea to synthesize progesterone are not known. The elephant may be extremely sensitive to the action of progesterone, or the hormone may not be necessary for normal reproduction in this species.
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