Effects of bovine follicular fluid and exogenous oestradiol on the GnRH-induced short luteal phase in anoestrous ewes.

The role of oestradiol in the control of premature luteolysis (previously shown to occur by the normal luteolytic mechanism involving PGF2 alpha and oxytocin) was investigated in anoestrous ewes induced to ovulate using GnRH (250 ng every 2 h for 24 h followed by 125 micrograms on day 0) without progesterone pretreatment. Seven ewes were administered charcoal stripped bovine follicular fluid (bFF) on days 1-5 (2 ml by s.c. injection every 8 h) together with oestradiol on days 2-4 (4 micrograms in 1 ml of corn oil by i.m. injection every 8 h). Ten ewes were treated with bFF and corn oil (as above), and ten ewes received saline and corn oil (control group). All ewes were treated with 1 microgram oxytocin (i.v.) on day 4 and plasma was collected for measurement of 13,14-dihydro-15-keto PGF2 alpha (PGFM). Blood samples were collected for measurement of progesterone and oestradiol (day--2 to 15). The ewes in the control group that responded to GnRH formed either normal (50% of ewes) or short-lived (50% of ewes) corpora lutea identified by progesterone profiles. The proportion of ewes that displayed premature luteolysis was reduced (P < 0.05) by bFF treatment alone (to 11% of ewes), and increased (P < 0.001) by bFF plus oestradiol treatment (to 100%). bFF treatment suppressed oestradiol concentrations (P < 0.01), whereas bFF plus oestradiol treatment increased oestradiol concentrations (P < 0.001) on days 1-5.(ABSTRACT TRUNCATED AT 250 WORDS)