Folicular development, concentrations of FSH, estradiol and MPGF2α associated with luteal persistence induced by the administration of steroid-free equine follicular fluid in the ewe

Abstract

THE ADMINISTRATION OF STEROID-FREE EQUINE FOLLICULAR FLUID (EFF) ON FOLLICULAR DEVELOPMENT, FSH, ESTRADIOL, MPGF2' AND LENGTH OF THE CYCLE WAS EVALUATED DURING DIESTRUS IN EWES. FORTY ONE PREVIOUSLY SYNCHRONIZED EWES WERE USED. TWO GROUPS WERE FORMED ON DAY 11 OF THE OESTROUS CYCLE: EFF GROUP (N = 24) RECEIVED 3 ML OF EFF IV EVERY 8 H UNTIL THE NEXT OESTRUS. THE CONTROL GROUP (N = 17) RECEIVED 3 ML IV OF SALINE SOLUTION EVERY 8 H UNTIL OESTRUS. PROGESTERONE LEVELS WERE DETERMINED IN DAILY BLOOD SAMPLES OBTAINED DURING THE OESTROUS CYCLE. FROM DAY 12 ONWARDS, FSH CONCENTRATION WAS DETERMINED IN BLOOD SAMPLES TAKEN AT 2 H INTERVALS IN 5 EWES OF EACH GROUP. IN SAMPLES FROM 2 EWES OF EACH GROUP, LEVELS OF MPGF2€˜ (PGF2' METABOLITE) WERE ALSO MEASURED. EIGHT EWES OF THE EFF GROUP AND 7 OF THE CONTROL GROUP WERE OVARIECTOMIZED ON DAY 14, IN ORDER TO MEASURE FOLLICULAR SIZE AND ESTRADIOL CONCENTRATION IN THE ASPIRATED FOLLICULAR LIQUID. LUTEAL PHASE AND LENGTH OF THE OESTROUS CYCLE WERE LONGER (P < 0.05) IN THE EFF GROUP (13.5 ± 0.53 AND 19.5 ± 0.66 DAYS RESPECTIVELY) THAN IN THE CONTROL GROUP (12.2 ± 0.32 AND 17.7 ± 0.26 DAYS RESPECTIVELY). FSH LEVELS WERE LOWER (P < 0.05) IN THE EFF GROUP THAN IN THE CONTROL ONE. FOLLICULAR SIZE AND ESTRADIOL WERE LOWER IN THE EFF GROUP (2.62 ± 0.14 MM; 4.35 ± 2.3 NG/ML) THAN IN THE CONTROL ONE (3.42 ± 0.20 MM; 34.8 ± 12.15 NG/ML). EWES IN THE CONTROL GROUP SHOWED 5 MPGF2' PULSES AT 8 ± 3.2 H INTERVALS FROM DAY 15 TO 17, WHEREAS ONE EFF EWE PRESENTED 5 PULSES BETWEEN DAYS 14 TO 17 AT 14 ± 2.3 H, INTERVALS AND THE OTHER EFF EWE HAD 4 PULSES FROM DAY 14 TO 20 AT 22 ± 12 H INTERVALS. IT IS CONCLUDED THAT EFF REDUCED FSH SECRETION THAT CAUSED THE PRESENCE OF SMALL FOLLICLES AND LOWER ESTRADIOL CONCENTRATIONS THAT LENGTHENED THE LUTEAL PHASE, PROBABLY THROUGH CHANGES IN THE PATTERN OF PGF2' SECRETION.