Uterine blood flow, myometrial activity and their response to adenosine during the peri-implantation period in sheep

Abstract

Summary. Uterine blood flow and myometrial activity were measured simultaneously in anaesthetized sheep 15 days after a sterile (non-pregnant group) or fertile (pregnant) mating. During the peri-implantation period uterine blood flow was similar in both groups of animals, but spontaneous myometrial activity was greatly reduced in pregnant ewes. This 'block' of myometrial activity was associated with circulating levels of progesterone which were significantly higher (2\m=.\8\ m=+-\0\m=.\8ng/ml, mean \m=+-\ s.e.m.) than those in non-pregnant animals (0\m=.\4 \m=+-\0\m=.\3 ng/ml). Adenosine injected into the uterine artery produced uterine vasodilatation in both groups, but the log dose\p=n-\response was significantly less in pregnant than in non-pregnant animals (P < 0\m=.\001).Myometrial activity was stimulated by adenosine, particularly in the pregnant group (P < 0\m=.\001

Development of Myometrial Electrical Activity during the First Half of Pregnancy in the Sheep

“…The contractile force generated in the myometrium by the intermittent impulses is probably minimal and is unlikely to raise intra-uterine pressure or have any mechanical effects on the embryo. Records of intrauterine pressure obtained from experiments on anaesthetized sheep at day 15 of pregnancy support this conclusion (Fleet and Heap 1982).…”

Purinergic Signalling in the Reproductive System

“…Myometrium P1 receptors are expressed by myometrial smooth muscle cells, including the A 2 in human myometrium membranes (Ronca-Testoni et al, 1984) and the A 2B subtype in the rat myometrium (Gillman and Pennefather, 1998). In rodents, adenosine, acting via P1 receptors, contracts the myometrium (Fleet and Heap, 1982;Smith et al, 1988;Schiemann et al, 1991). A 1 receptors mediate excitatory responses during the proliferation phase of the menstrual cycle, while A 2 receptors mediate relaxation largely during the secretory phase (Fleet and Heap, 1982;Samuelson et al, 1985).…”

“…In rodents, adenosine, acting via P1 receptors, contracts the myometrium (Fleet and Heap, 1982;Smith et al, 1988;Schiemann et al, 1991). A 1 receptors mediate excitatory responses during the proliferation phase of the menstrual cycle, while A 2 receptors mediate relaxation largely during the secretory phase (Fleet and Heap, 1982;Samuelson et al, 1985). In the female, adenosine is a prejunctional modulator of adrenergic neurotransmission to the uterus (Wiklund et al, 1986).…”

Uterine Blood Flow during Early Pregnancy in Ewes: Interaction between the Conceptus and the Ovary Bearing the Corpus Luteum

“…Greiss and Anderson (1970) observed a transient increase in uterine BF between d 13 to 15 postmating for some of the ewes in their study. Others, however, have been unable to demonstrate this transient increase in uterine BF (Fleet and Heap, 1982). The results of Fleet and Heap (1982) may have been obtained because blood flow was only recorded for the nonluteal, nonpregnant uterine horn.…”

“…Others, however, have been unable to demonstrate this transient increase in uterine BF (Fleet and Heap, 1982). The results of Fleet and Heap (1982) may have been obtained because blood flow was only recorded for the nonluteal, nonpregnant uterine horn.…”