The metabolism and pattern of excretion of urinary steroids during oestrus and pregnancy in the Giant panda is described. Three female pandas from the London, Washington and Madrid Zoos were studied over different periods between March 1980 and September 1982.
High pressure liquid chromatography and sequential enzyme hydrolysis indicated that oestrone glucuronide was the most abundant urinary oestrogen metabolite during oestrus. Levels of conjugated oestrone in late pregnancy, however, were low and similar to those of conjugated oestradiol-17β
There was a rapid increase in the excretion of conjugated oestrone to reach maximum levels during late pro-oestrus; oestrus occurred when levels of conjugated oestrone were declining. The measurement of oestrone-3-glucuronide by direct, non-extraction assay provides a rapid and reliable method for detecting oestrus and ovulation in the Giant panda.
Artificial insemination of the London and Madrid pandas was performed in 1981 and 1982, respectively. The Madrid panda gave birth to twin cubs after a gestation period of 159 days. Levels of urinary oestrone conjugate remained low throughout pregnancy. There was no increase in the excretion of pregnanediol-3α-glucuronide (assumed to be an urinary metabolite of progesterone) until approximately day 120 when a rapid, five-fold increase in levels occurred. The levels of pregnanediol-3α-glucuronide remained elevated for approximately three weeks after which there was a gradual decline beginning two-and-α-half weeks before parturition. Measurement of pregnanediol-3α-glucuronide enables the detection of pregnancy after three to four months and should also be useful in predicting parturition. A delay of implantation during pregnancy in the Giant panda is suggested.
There was no consistent elevation in pregnanedioI-3α-glucuronide excretion in the five months after artificial insemination of the London panda, despite a marked increase in circulating progesterone of ovarian origin. Pregnancy could not be confirmed from external examination of the uterus at laparotomy; histological examination of biopsy material revealed advanced endometrial hyperplasia.