Dynamic progesterone responses to simulation of a natural pulse of a metabolite of prostaglandin F2α in heifers

Shrestha, Hemanta; Beg, M.A.; Siddiqui, M.A.R.; Ginther, O.J.

doi:10.1016/j.anireprosci.2009.06.021

Cited by 22 publications

(30 citation statements)

References 23 publications

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“…luteolytic dose of PGF, but an increase that appeared to occur by 20 min after the beginning of i.u. infusion to simulate a PGFM pulse was not significant (Shrestha et al 2010).…”

Section: Introductionmentioning

confidence: 99%

“…A dose of PGF or a PGF analogue that induces complete luteolysis with a single treatment causes an immediate transient increase in progesterone prior to the decrease (Lamond et al 1973, Hixon & Hansel 1974, Skarzynski et al 2003. The transient increase is reportedly a non-physiologic response to a pharmacologic dose of PGF in heifers (Ginther et al 2009a, Shrestha et al 2010 and mares (Ginther et al 2007a(Ginther et al , 2009c. In a study with a limited number of heifers per group, an initial transient increase in progesterone occurred 10 min after a single bolus i.u.…”

Section: Introductionmentioning

confidence: 99%

“…The temporal relationship between the immediate (within 10 min) transient progesterone increase and luteal blood flow after a pharmacologic dose of PGF is unknown. Furthermore, an immediate increase in progesterone during a simulated PGFM pulse has not been adequately investigated, owing to the limited number of heifers (nZ4/group) in the only available report (Shrestha et al 2010).…”

Section: Introductionmentioning

confidence: 99%

“…In addition, a pronounced transient progesterone rebound began at 1 h during a 2-h i.u. infusion of PGF to simulate a PGFM pulse (Shrestha et al 2010); the progesterone decrease after the rebound was followed by progesterone resurgence, so that the interval to ovulation was not shortened by the single simulated pulse. The relationship of the progesterone rebound with the changes in luteal blood flow has not been determined.…”

Section: Introductionmentioning

confidence: 99%

“…Three hypotheses were tested in heifers in the present experiment: 1) a transient increase in progesterone occurs during infusion of PGF to simulate a natural PGFM pulse, which is based on a reported increase that did not reach significance but with a limited number of heifers (Shrestha et al 2010); 2) the luteal blood flow increase after a single luteolytic dose of PGF accompanies the progesterone decrease, which is based on a rationale from Acosta et al (2002) and 3) the immediate response of circulating hormones, other than progesterone, to a single completely luteolytic dose of PGF does not occur during a simulated pulse of PGFM, which is based on a rationale primarily from a study in mares (Ginther et al 2009c). In addition, we determined the temporal relationships between changes in progesterone concentrations and changes in luteal blood flow during and until 4 h after a 2-h simulated PGFM pulse.…”

Section: Introductionmentioning

confidence: 99%

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Luteal blood flow and concentrations of circulating progesterone and other hormones associated with a simulated pulse of 13,14-dihydro-15-keto-prostaglandin F2α in heifers

Shrestha¹,

Beg²,

Imam³

et al. 2010

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Progesterone and luteal blood flow effects of an i.u. 2-h infusion of 0.25 mg/h of prostaglandin F 2a (PGF) that simulated a natural pulse of 13,14-dihydro-15-keto-PGF (PGFM) were compared to the effects of a single bolus i.u. injection of PGF (4 mg) that induced complete luteolysis in heifers. Blood sampling and an estimate of the percentage of luteal area with colour-Doppler signals of blood flow were performed every 2 min for 20 min and less frequently thereafter for 6 h. After the beginning of PGF infusion or a bolus injection, progesterone increased to a peak at 14 and 10 min respectively, and was accompanied by an increase in blood flow in the bolus group but not in the infusion group. Progesterone then decreased for 1 or 2 h and was accompanied by a continued elevation in blood flow in the PGF bolus group and by a slight increase in the PGF infusion group. Progesterone then rebounded in both groups, but the rebound was greater in the infusion group. Blood flow decreased during the descending arm of the progesterone rebound. Cortisol and prolactin began to increase 6 min after the bolus PGF injection but did not increase during or after PGF infusion. The increases in cortisol, prolactin and blood flow after a PGF bolus treatment but not during a simulated PGFM pulse indicated that the bolus treatment was pharmacologic, and its use may lead to faulty conclusions on the nature of physiologic luteolysis. The comparisons between progesterone and blood flow are novel.

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“…luteolytic dose of PGF, but an increase that appeared to occur by 20 min after the beginning of i.u. infusion to simulate a PGFM pulse was not significant (Shrestha et al 2010).…”

Section: Introductionmentioning

confidence: 99%