PGFM response to exogenous oxytocin and determination of the half‐life of oxytocin in nonpregnant mares

Paccamonti, D.; Pycock, Jonathan F.; Taverne, M.A.M.; Bevers, M.M.; Weijden, G.C. van der; Gutjahr, S.; Schams, D.; Blouin, D.

doi:10.1111/j.2042-3306.1999.tb03818.x

Cited by 35 publications

(24 citation statements)

References 16 publications

(14 reference statements)

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“…For the current study the half-life of oxytocin in cycling, non-pregnant mares was determined to be 5.89 minutes, which differed minimally from the half life of 6.8 min reported by Paccamonti et al [23].…”

Section: Discussionmentioning

confidence: 63%

Ex vivo influence of carbetocin on equine myometrial muscles and comparison with oxytocin

et al. 2012

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In order to determine the inter-cyclic effect of oxytocin and carbetocin on equine myometrial tissue, the effect of the drugs was evaluated through pharmacokinetic and pharmaco-dynamic studies. The complete pharmacokinetic profile for oxytocin was unknown and had to be established. To do so, 25 IU of oxytocin were administered intravenously to six cycling mares and blood samples were collected before and 2, 4, 8, 2 and 15 min after administration. The half-life of oxytocin was determined to be 5.89 min, the clearance rate 11.67 l/min, MRT 7.78 min, T max 2 min, and C max 0.51 ng/ml. The effective plasma concentration was estimated to be 0.25 ng/ml. This was similar to the concentration achieved for the organ bath study where the EC 50 was calculated at 0.45 ng/ml. To determine the inter-cyclic effect of oxytocin and carbetocin uterine myometrial samples were collected from slaughtered mares in oestrus, dioestrus and anoestrus. The samples were mounted in organ baths and exposed to four ascending, cumulative doses of oxytocin and carbetocin. Area under the curve and amplitude, E max and EC 50 were studied for each agonist and statistically evaluated. The effect of oxytocin on equine myometrial tissue was higher during dioestrus, and surprisingly anoestrus, than during oestrus, whereas the effect of carbetocin was the same independent of the stage of oestrous cycle. A significant difference was found for oestrous and anoestrous samples when oxytocin was used but not when carbetocin was used.

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Section: Discussionmentioning

confidence: 63%

Ex vivo influence of carbetocin on equine myometrial muscles and comparison with oxytocin

et al. 2012

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“…In previous studies on the effect of exogenous OT on PGFM in mares, the doses were apparently based on clinical recommendations (e.g., 20 IU to evacuate the uterus [17]). Treatment of nonpregnant mares with OT doses of 10 to 25 IU [18][19][20][21] or the OT response to uterine biopsy [22,23] stimulates an increase in PGFM. The OT treatments are especially effective near the expected day of luteolysis when the number of uterine OT receptors is maximum (Days 14-17) [22][23][24].…”

Section: Introductionmentioning

confidence: 99%

Oxytocin induction of pulses of a prostaglandin metabolite and luteolysis in mares

et al. 2015

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“…A series of exogenous stimuli such as manual manipulation of clitoris, vagina and cervix, intrauterine infusion of PBS and uterine biopsies (Nikolakopoulos et al 2000, Paccamonti et al 1999, Sharp et al 1997) have been shown to induce oxytocin (OT) secretion in mares. In our study (Handler et al 2003), cervical dilation stimulated distinct secretion of OT up to maximum plasma concentrations (305.2 pg/mL) compared with insertion (125.5 pg/mL) and controls (6.1pg/mL).…”

Section: Cyclic Maresmentioning

confidence: 99%

Endocrine responses to standardized cervical manipulation in the mare

Handler¹

2008

PHK

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IntroductionManipulations of the cervix are a prerequisite for numerous diagnostic and therapeutic techniques in equine gynaecology, obstetrics and reproductive biotechnology such as endometrial swabs, cytology and biopsies, palpation of the vaginal portion of the cervix, intrauterine insemination and instillation, therapeutic uterine flushing, embryo collection and transfer, and surgery of the cervix. Depending on the reproductive status of the mare, knowledge of the effects of cervical manipulations would allow avoiding negative consequences for the reproductive success in mares.The effects of cervical manipulations on oestrous cycle and early pregnancy in the mare have been under discussion for decades. Insertion of aluminum rods into the cervical canal did not change oestrous cycle patterns (Arthur 1975). In contrast, Hurtgen (1975), Hurtgen and Whitmore (1978) and Hurtgen and Ganjam (1979) were able to shorten dioestrus in mares by simply dilating the cervix manually. Moreover, Berglund et al. (1982) SummaryThe impact of manipulations of the equine cervix on the endocrine system, oestrous cycle patterns, pregnancy rates and embryonic development was investigated by six studies in cyclic and inseminated pregnant mares. In cyclic mares, standardized cervical dilation at Day 7 after ovulation (Day 0 = ovulation) shortened luteal phase and oestrous cycle by almost 2 days. Cervical dilation did not provoke an immediate release of PGF2α, but stimulated a distinct secretion of oxytocin. Starting from Day 10, dilated mares showed significantly lower progesterone levels and went two days earlier into luteolysis compared with controls. Administration of xylazine hydrochloride blocked the oxytocin release completely and oestrous cycle length was not altered by combined treatments. In inseminated, pregnant mares, dilation of the equine cervix did not affect pregnancy rates and early embryonic growth rates. Cervical manipulation also stimulated the secretion of oxytocin, but plasma levels of progesterone did not vary among groups. In contrast, dilated mares treated with xylazine hydrochloride did not secrete oxytocin, but progesterone levels tended to be lower compared with untreated controls (xylazine hydrochloride only). Surprisingly, embryonic growth rates were significantly higher in dilated mares pretreated with xylazine hydrochloride compared with controls. Cervical dilation did not change plasma concentration patterns of LH and prolactin with one exception. Only one pregnant mare showed a distinct rise of prolactin after cervical dilation. Moreover, this mare was the only one, which developed endometrial inflammation and subsequent embryonic death by Day 12. This observation needs to be investigated further for clarification of a possible contribution of prolactin to the mechanisms involved. Additionally, the role of xylazine has to be evaluated, because there is no further evidence from our data that the inhibition of oxytocin release is of significance concerning the effects on embryonic growth by combined tre...

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PGFM response to exogenous oxytocin and determination of the half‐life of oxytocin in nonpregnant mares

Cited by 35 publications

References 16 publications

Ex vivo influence of carbetocin on equine myometrial muscles and comparison with oxytocin

Ex vivo influence of carbetocin on equine myometrial muscles and comparison with oxytocin

Oxytocin induction of pulses of a prostaglandin metabolite and luteolysis in mares

Endocrine responses to standardized cervical manipulation in the mare

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