Pulsatile secretion of gonadotrophins, ovarian steroids and ovarian oxytocin during the luteal phase of the oestrous cycle in the cow
- 1 July 1984
- journal article
- research article
- Published by Bioscientifica in Reproduction
- Vol. 71 (2), 479-491
- https://doi.org/10.1530/jrf.0.0710479
Abstract
All hormones were determined in blood samples collected simultaneously from the caudal vena cava and jugular vein at 20-min intervals for 12 h during the early (day 4) and mid- (.apprx. day 11) luteal phases of the estrous cycle in 7 cows. Mean concentrations of estradiol, progesterone and oxytocin were greater (P < 0.01) in the vena cava than in the jugular vein. Pulses of these hormones were also more easily identifiable in the vena cava. The frequency of LH [luteinizing hormone] pulses was higher (P < 0.01) during the early luteal than during the mid-luteal phase (8.0 vs. 3.6 pulses/12 h). During both phases, 90-96% of all LH pulses were followed within 60 min by a pulse of estradiol. Basal concentration and amplitude of estradiol pulses were greater (P < 0.05) during the early than during the mid-luteal phase. The frequency of FSH pulses was similar to that of LH during the early luteal phase (8.5 and 8.0 pulses/12 h), but was greater (P < 0.01) than that of LH during the mid-luteal phase (6.3 vs. 3.6 pulses/12 h). Thus, 41% more (P < 0.01) FSH pulses than LH pulses were observed during the mid-luteal phase. The separate FSH pulses were associated with low-amplitude short-duration pulses of LH as clarified by an additional study (in 3 cows) using 5-min sampling intervals: 90-100% of all LH/FSH pulses and separate FSH pulses were secreted either concomitantly with or followed by a pulse of progesterone. No separate FSH pulses were associated with a pulse of estradiol. Basal concentration and amplitude of progesterone were greater (P < 0.01) during the mid-luteal than during the early luteal phase. The frequency of oxytocin pulses was similar to that of progesterone during the mid-luteal but not during the early luteal phase. During the mid-luteal phase 97% of all oxytocin pulses were associated with a pulse of progesterone. Separate FSH pulses evidently are secreted in addition to parallel LH and FSH pulses during the mid-luteal phase; therefore, the frequency of secretion of LH may be modulated to a greater extent by ovarian steroids than is FSH pulse frequency. Pulses of progesterone are probably a result of stimulation by pulses of FSH and/or LH whereas pulses of estradiol are caused by LH pulses. Ovarian oxytocin and progesterone are secreted concomitantly during the mid-luteal phase of the estrous cycle.This publication has 3 references indexed in Scilit:
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- Relationships between short-term variations of LH, FSH, prolactin and testosterone in peripheral plasma of prepubertal bullsReproduction, 1978