Cervical Dilatation Related to Uterine Electromyographic Activity and Endocrinological Changes During Prostaglandin F2α-Induced Parturition in Cows

Abstract

The temporal relationship between changes in cervical dilatation, uterine electromyographic (EMG) activity, and maternal plasma concentrations of estradiol 17beta (E(2)), progesterone (P(4)), and 13,14-dihydro-15-keto-prostaglandin-F(2alpha) (PGFM), was investigated in six parturient cows. Calving was induced with a single injection of a synthetic analogue of prostaglandin F(2alpha) (PG) on Day 274 of gestation. Cervical dilatation was measured continuously by measuring the transit time between two implanted ultrasound crystals while at the same time uterine EMG activity was measured through two silver electrodes sutured on the myometrial surface until the expulsive stage of calving had been reached. In blood samples collected at 4-h intervals, starting at the moment of PG injection, the mean plasma E(2) concentration gradually increased and was significantly elevated at 28 h after PG injection. At 4 h after PG treatment, the mean P(4) concentration had dropped significantly and continued to decrease until a value of around 1 ng/ml was reached, where it stayed until the onset of expulsion. Mean plasma PGFM concentrations increased steadily after PG injection, reaching significantly elevated concentrations at 20 h after treatment. In the five cows that delivered calves in anterior positions, uterine EMG activity, expressed as root mean square (RMS in microV), started to increase at a mean interval (+/- SD) of 13.1 +/- 3.7 h following PG treatment. The increase in EMG activity was significantly correlated with changes in plasma PGFM concentrations. In these cows, dilatation of the caudal cervix started after a mean (+/- SD) interval of 28.5 +/- 1.5 h following PG treatment and dilatation progressed at a mean (+/- SD) rate of 2.25 +/- 0.24 cm/h. In one cow with a calf in the posterior position, uterine EMG activity and dilatation started at 15.8 h and 31.8 h, respectively, after induction of calving. We conclude that a predictable sequence of physiological changes occurs around induction of calving, which allows specific timing of future studies on cellular and biochemical changes within the cervix during parturition.

Cervical diameter in relation to uterine and cervical EMG activity in early postpartum dairy cows with retained placentas after PGF2alpha induced calving

“…At that time, 15 out of 16 cows showed a cervical diameter of between 14 and 20 cm. [15,24,27]. Also others described a cervical diameter of 20 cm at 1.5 h after spontaneous parturition [25].…”

“…They were selected on the following traits: a body condition score of 3-3.5 [26], only spontaneous uncomplicated parturitions in their history and carrying a singleton pregnancy with an anterior presentation. Six cows were deemed to be sufficient for this study, based on previous studies using similar physiological parameters and experimental protocol [14,15,24,27]. The use of these animals in this experiment which was a follow-up of a previously described study [24] had been approved by the Ethical Committee of the Veterinary Faculty of Utrecht University (The Netherlands).…”

“…They underwent surgery 10-14 days before parturition was induced with a synthetic PGF2a analogue (Prosolvin 1 , 2 ml i.m., Intervet, Boxmeer, The Netherlands) on day 274 of pregnancy. The surgical procedure has been extensively outlined previously [24,27]. Briefly, during abdominal surgery, two bipolar AgAgCl electrodes, made in our own laboratory with 5 mm distance in between [28], were sutured on the surface of the uterine myometrium near the top of the uterine horn.…”

Excess estrogen sulfoconjugation as the possible cause for a poor sign of parturition in pregnant cows carrying somatic cell clone fetuses

“…Uterine contraction is essential for the process of parturition, and placental estrogens influence the activity of the uterine myometrium (Wathes & Porter 1982). Also, placental estrogens may dilate the cervix that allows passage of the fetus through the birth canal (Breeveld-Dwarkasing et al 2003). Estrogens are synthesized by aromatase (CYP19), which converts androgens into estrogens in fetal cotyledonary tissue (Schuler et al 2006), and show a dramatic increase in maternal plasma during the prepartum period (Takenouchi et al 2004).…”

Prepartum Maternal Plasma Glucose Concentrations and Placental Glucose Transporter mRNA Expression in Cows Carrying Somatic Cell Clone Fetuses

“…The secretion of cortisol from the fetal adrenal cortex is facilitated particularly during the last week of gestation and reaches a peak just before parturition [5]. In the placenta, cortisol promotes the synthesis of estrogens that induce relaxation and dilation of the birth canal [7]. Furthermore, cortisol downregulates fetal growth and stimulates the maturation of those organs essential for extrauterine survival, such as the lungs and thyroid [8].…”