CHANGES IN PLASMA-CONCENTRATIONS OF LUTEINIZING-HORMONE, PROGESTERONE, AND TESTOSTERONE IN TURKEY HENS DURING THE OVULATORY CYCLE

Changes in luteinizing hormone (LH), progesterone, and testosterone co ncentrations were determined in blood samples taken every 10 min for 2 6 hr during an ovulatory cycle in laying turkey hens. During the 26-hr sampling period, one peak of both LH and progesterone and numerous pe aks of testosterone were detected. The concentration of LH in plasma i ncreased from basal level (2.44-4.0 ng/ml) to maximum level (8.57-24.3 ng/ml) over 1 to 2 hr and then declined over 3 to 5 hr to a basal lev el. The duration of the descending portion of the peak was about doubl e that of the ascending portion. The concentration of progesterone inc reased rapidly from a basal level of 1.18-1.65 ng/ml to a peak of 6.18 -11.87 ng/ml and then maintained a plateau before rapidly declining to basal level. The concentration of testosterone increased from a basal level of 0.06-0.09 ng/ml to a peak level of 0.13-0.30 ng/ml. All maxi mum levels of testosterone preceded those of LH, and all maximum level s of LH preceded those of progesterone. The durations of the progester one peaks were longer than those of the LH peaks. Progesterone concent rations returned to basal level after LH had returned to basal level, although the initial increase in progesterone concentration was earlie r, later, or at the same time as LH. Peak durations of testosterone we re variable. The preovulatory surges of LH and progesterone of five of nine sets of samples started at the end of the scotophase and ended d uring the beginning portion of the photophase. In three of nine sets b oth the start and the end occurred during the scotophase and in one of nine sets during the photophase. It was concluded from this study tha t the patterns of secretion of LH, progesterone, and testosterone were similar in that the preovulatory surge was superimposed on a relative ly stable basal level, while the temporal relationships of the ovulato ry surges of these hormones were variable. The preovulatory surges wer e more tightly associated with ovulation rather than with photoperiod. Neither progesterone nor testosterone might be an initiator of the LH surge prior to ovulation. (C) 1997 Academic Press.