title: Pulses of prolactin before, during, and after luteolysis and synchrony with pulses of a metabolite of prostaglandin F2α in heifers.
abstract: Pulses of prolactin (PRL) and a metabolite of prostaglandin F2α (PGFM) were determined from hourly blood samples collected before, during, and after luteolysis (n=7 heifers). Progesterone concentrations were used to partition the results into six 12-h sets from 12h before to 36h after luteolysis. Pulses of PRL with a nadir-to-nadir interval of 4.4±0.2h were detected in each 12-h set. Pulses were rhythmic (P<0.05) in six heifers, beginning 12h before the end of luteolysis. The peak of a PRL pulse was greater (P<0.05) for the 12h after the end of luteolysis than for other 12-h sets, except for the last set of luteolysis. Area under the curve of a pulse was greater (P<0.05) for the 24h that encompassed the end of luteolysis than for two previous 12-h sets. Synchrony between the peaks of PRL and PGFM pulses was greater (P<0.03) during and after luteolysis (same hour for 29/39 pairs) than before luteolysis (0/12). Concentration of PRL centralized to the peak (Hour 0) of PGFM pulses was greater (P<0.05) at Hours 0 and 1 than at Hours -2, -1, and 3. Results supported the hypothesis that PRL is secreted in pulses in heifers. The pulses were most prominent and rhythmic during the last 12h of luteolysis and thereafter. The pulse peaks of PRL and PGFM were synchronized for most PRL pulses during and after luteolysis.
authors.affiliation: Eutheria Foundation, Cross Plains, WI 53528, USA. ginther@vetmed.wisc.edu
authors.forename: O J
authors.initials: OJ
authors.lastname: Ginther
authors.forename: M A
authors.initials: MA
authors.lastname: Beg
mesh_terms: D000818:Animals; D002417:Cattle / Q000097:blood* / Q000378:metabolism*; D015237:Dinoprost / Q000097:blood* / Q000378:metabolism*; D005260:Female; D003341:Luteolysis / Q000502:physiology*; D011374:Progesterone / Q000097:blood / Q000378:metabolism; D011388:Prolactin / Q000097:blood / Q000378:metabolism*; D013997:Time Factors
chemical_list: D011374:Progesterone; D011388:Prolactin; D015237:Dinoprost