Effect of the oestrous cycle, pregnancy and uterine region on the responsiveness of the isolated mouse uterus to prostaglandin F2α and the thromboxane mimetic U46619

Abstract

Previous studies in this laboratory have suggested that the isolated uterus from non-pregnant mice has a prostaglandin F and a thromboxane receptor population similar to that found in human myometrium. The aim of this study was to investigate any regional variation in myogenic activity and responsiveness to prostaglandin F 2 (PGF 2 ) and the thromboxane mimetic U46619 in the mouse uterus taken during different stages of the oestrous cycle and during pregnancy. Uterine samples from BKW mice were taken from different anatomical segments along the length of each uterine horn and set up for superfusion at 2 ml/min with Krebs solution (containing 1 µM indometacin) at 37 C, and gassed with 95%O 2 /5%CO 2 . Responses (area under the curve) are expressed as a percentage of the final contraction induced by hypotonic shock. Data are expressed as the means S.E.M.of n=5-12 and were analysed using Student's paired t-test or two-way ANOVA with a Bonferroni post hoc test. Regional variation in myogenic activity was observed in all tissues studied except those taken during labour. These tissues displayed significantly greater myogenic activity than tissues taken at late gestation and at all stages of the oestrous cycle. Tissues from pregnant animals were generally more responsive to U46619 and PGF 2 than tissues taken from non-pregnant animals. Tissues taken from the upper segment of the uterine horn were more responsive to both agonists during the oestrous cycle. The findings demonstrated that the hormonal milieu and site of excision are important for myogenic activity and responsiveness.

Uterine Contractility in the Nonpregnant Mouse: Changes During the Estrous Cycle and Effects of Chloride Channel Blockade1

“…Spontaneous contractility of the cycling non-pregnant uterus has also been studied in the rat [40][41][42][43], guinea pig [44], dog [45], cow [46][47][48][49] and horse [50,51]. We have revealed that despite considerable variability in contractile behaviors, there are certain motility patterns that are more prevalent at each phase of the cycle; changes which likely correspond to the cyclic variation in the levels and receptor expression of ovarian steroid hormones, estrogen and progesterone, which have been shown to modulate spontaneous contractility in vitro [52][53][54][55][56] and in vivo [41][42][43]57]. Contractions predominately initiated from the oviduct end suggesting this was the dominant pacemaking site, as has been reported by others [41].…”

A Dominant Loss-of-Function GJA1 (Cx43) Mutant Impairs Parturition in the Mouse1

“…There was a 10-min interval between each application of oxytocin. At the end of each experiment, the superfusate was changed from KRB solution to distilled water to induce a large contraction of the tissue (hypotonic shock) [23,24], which was used as a reference contraction (100%).…”

Smooth Muscle Pharmacology in the Isolated Virgin and Pregnant Rat Uterus and Cervix

“…Oxytocin is an inducer of labor (Smith and Merrill, 2006;Arthur et al, 2007) as are prostaglandins (Goureau et al, 1992;Griffiths et al, 2006). Responsiveness of the human cervix to prostaglandins is one of the better- characterized responses for cervical smooth muscle.…”

“…Use of the isometric contractile technique limits studying this tissue in a coordinated fashion. Second, studies suggest regional differences in the upper and lower uterus (Griffiths et al, 2006), and we have used a preparation that extends into both the upper and lower uterus (but excluding the cervical uterus). A third and final limitation is that we used only carbamylcholine as the contractile agonist when investigating the effects of relaxant substances.…”