PULSATILITY OF SYSTEMIC FSH AND LH CONCENTRATIONS DURING FOLLICULAR-WAVE DEVELOPMENT IN CATTLE

Changes in systemic FSH and LH pulsatility in temporal association wit h follicular-wave emergence and follicle deviation were studied in cat tle. Wave emergence was defined as occurring when the future dominant follicle first reached 4 mm, as established retrospectively. Follicle deviation was defined as the beginning of a change in growth rates bet ween the 2 largest follicles and occurred 60.4 +/- 4.2 h after wave em ergence. Follicles were tracked by transrectal ultrasound scanning eve ry 8 h, and blood samples for pulse characterization were collected ev ery 20 min from before emergence until after deviation. Pulses were ch aracterized by the Pulsar program applied to each 8-h increment, cente red on the hour of follicle scanning in each heifer (n=6). Pulsatility of FSH was not detected for any of the 8-h increments. The mean FSH c oncentrations for the 24 samples per 8 h increased (P<0.05) between 8 h before and 8 h after wave emergence, followed by a decrease 40 to 16 h before deviation. The low mean values continued for 24 h after devi ation. Pulses of LH were detected for all 8-h increments. The LH mean of all concentrations per 8 h and pulse frequency increased (P<0.05) b etween the hour of wave emergence and 32 h after emergence and then pu lse frequency plateaued at a mean interpeak interval of 1.3 h. Increas ed LH means for all concentrations per 8 h and basal concentration wer e reached 32 h before deviation. The results indicated that elevated c oncentrations of LH and reduced concentrations of FSH were present 32 to 16;h before to at least 24 h after the beginning of follicle deviat ion. However, an abrupt, short-term change in FSH concentrations or in LH pulsatility in close temporal association with follicle deviation that could act as an acute stimulus to initiate deviation was not foun d. (C) 1998 by Elsevier Science Inc.