Interrelationships between endocrine changes in peripheral and uterine-venous blood and uterine activity at parturition in the pig

Randall, G. C. B.; Taverne, M.A.M.; Challis, J. R. G.; Kendall, June Z.; Tsang, Benjamin K.

doi:10.1016/0378-4320(86)90131-4

Cited by 13 publications

(4 citation statements)

References 36 publications

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“…The nature of the signal initiating the release of relaxin is unlikely to come from the uterus, since the timing of the surge of relaxin was identical in both hysterectomized sows and sows in late pregnancy (Anderson, Adair, Stromer & McDonald, 1983). These data, together with the findings of Gooneratne, Bryant-Greenwood, Maule-Walker et al (1983) and Randall, Taverne, Challis et al (1986), question the role of uterine PGF2a as the natural and initial luteolytic agent (First & Bosc, 1979). It has therefore been suggested that small amounts of intra-luteal PG (Rothchild, 1981;Patek & Watson, 1983) may be responsible for the regression of the corpus luteum and thus may not be detected in the peripheral circulation by conventional radioimmunoassay.…”

Section: Discussionmentioning

confidence: 69%

Initiation of parturition and lactation in the sow: effects of delaying parturition with medroxyprogesterone acetate

Whitely

Hartmann²,

Willcox³

et al. 1990

Journal of Endocrinology

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The synthetic progestagen, medroxyprogesterone acetate (MPA), was administered to sows in late pregnancy with the objective of slightly delaying the time of farrowing and thereby providing more marked associations between hormonal changes and the termination of pregnancy, and the initiation of farrowing and lactation in this species. MPA was administered orally (140 mg, twice daily) to eight sows in late pregnancy on days 112, 113 and 114 of gestation. Parturition was then induced to occur on day 116 by injecting 200 micrograms cloprostenol i.m. on day 115 of gestation. The peripartum changes in the plasma concentrations of progesterone, cortisol, oestradiol-17 beta, relaxin, prolactin, lactose and 13,14-dihydro-15-keto prostaglandin F2 alpha (PGFM) were measured in these sows together with a group of untreated sows. The gestational length for the MPA-treated sows (116.3 +/- 0.3 days, mean +/- S.E.M.) was significantly (P less than 0.01) greater compared with the untreated sows (114.9 +/- 0.3 days). Plasma progesterone declined earlier (P less than 0.05) with respect to the time of parturition in the treated sows compared with the untreated group. With respect to the timing of parturition, the time at which maximal concentrations of relaxin were attained and the timing of the subsequent decline were earlier in the MPA-treated sows. In both groups of sows, the concentration of relaxin increased before the decline in plasma progesterone. In the untreated sows, the concentration of PGFM increased either slightly before or at the same time as the decline in plasma progesterone, whereas in sows treated with MPA, progesterone concentrations began to decline before any significant increase in the plasma concentration of PGFM. The profiles of cortisol, oestradiol-17 beta and PGFM were similar in both groups of sows. In both groups of sows, the timing of the initial increase in the concentration of plasma prolactin coincided with a similar rise in plasma lactose (P less than 0.01). Plasma progesterone either declined earlier or at the same time as the rise in plasma lactose (P less than 0.01) in the treated group of sows only. We conclude that since the prepartum changes in the concentration of progesterone and relaxin occurred before significant changes in the concentration of PGFM in the MPA-treated sows, the nature of the luteolytic factor and the mechanism by which it exerts its action remains obscure. The higher concentration of lactose in the mammary secretion at birth in the MPA-treated sows compared with the untreated group suggested that lactogenesis was initiated earlier with respect to parturition following MPA treatment.(ABSTRACT TRUNCATED AT 400 WORDS)

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Section: Discussionmentioning

confidence: 69%

Initiation of parturition and lactation in the sow: effects of delaying parturition with medroxyprogesterone acetate

Whitely

Hartmann²,

Willcox³

et al. 1990

Journal of Endocrinology

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“…The drop of progesterone and the rise of oestrogens just prior to parturition in pigs has been described in peripheral plasma [for references, see Kindahl et al, 1982] and also in blood collected from the uterine artery and vein [Randall et al, 1986]. Also, an increase in prostaglandin F2(V (PGF2c[) in the uterine vein has been observed 8-24 h before delivery of the first piglet ¡Randall et al., 1986].…”

Section: Discussionmentioning

confidence: 99%

Morphology of the Porcine Myometrium during Parturition

Thilander

Rodriguez‐Martinez²

1990

Cells Tissues Organs

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The ultrastructure of the porcine myometrium collected at well-defined stages during parturition was investigated by transmission electron microscopy. The morphology of the parturient myometrium resembled in general that in pregnant and non-pregnant pigs. The diameter of the smooth muscle cells was however about twice that of non-pregnant myometrium. Thick myofilaments were numerous. The number of caveolae seemed to be higher in parturient compared with non-pregnant and pregnant cells. Gap junctions occurred richly and were large, while the intrinsic innervation was very scanty. To conclude, the endocrinological changes in the pig taking place just prior to parturition, are translated into morphological changes by stimulating the formation of uterine gap junctions. This provides low-resistance pathways between the muscle cells and activates the myometrium for the delivery process.

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“…The effects of prosta¬ glandin on the hormonal cascade are unclear. Its luteolytic action during the cycle and pregnancy has been proven (Diehl et al, 1977), but at term the rise in prostaglandin concentration follows rather than precedes the fall in progesterone concen¬ tration (Randall et al, 1986;Watts et al, 1988). Prostaglandin F2a is also closely connected to the myometrial activity at parturition (Randall, 1990).…”

Section: Wintermentioning

confidence: 99%