Uterine oxytocin receptors in cyclic and pregnant cows

Abstract

Binding of [3H]oxytocin to uterine subcellular preparations ('oxytocin receptor concentrations') was measured in uterine tissue of heifers and multiparous dairy cows at various stages of the oestrous cycle and during early pregnancy. A method for the assay of ovine uterine oxytocin receptors was optimized for use on bovine tissue. Oxytocin receptor concentrations were increased in cyclic animals around the period of luteolysis and oestrus, rising on Day 15 in endometrium and on Day 17 in myometrium while pregnant animals showed no comparable rise. Receptor concentrations then declined on Day 3 after oestrus in myometrium and on Day 5 in endometrium. Some cyclic animals did not show the expected rise in receptors in the late luteal phase; these animals had abnormally high progesterone concentrations for this stage of the cycle. In animals slaughtered on Day 18 after oestrus and/or insemination which had low oxytocin receptor levels, plasma progesterone concentrations were consistently high; while all animals showing the late luteal phase elevation in receptor values had low progesterone concentrations. Oxytocin receptor and progesterone concentrations were negatively correlated (P less than 0.05). These data support the hypothesis that oxytocin receptor level is a key factor in the process of luteolysis in cattle and that in pregnancy there is suppression of uterine oxytocin receptor at the expected time of luteolysis. We suggest that uterine oxytocin receptor levels are partly controlled by circulating steroid hormones and are suppressed during early pregnancy.

The effect of pregnancy on the expression of uterine oxytocin, oestrogen and progesterone receptors during early pregnancy in the cow

“…This implied that there was a slight temporal delay in the translation of the mRNA into protein. The timing is consistent with a previous study in the cow using radioreceptor assays in which the rise in oxytocin receptors was reported to occur on day 15 ( Jenner et al 1991). Furthermore, injection of oxytocin to non-pregnant cows failed to release PGF 2 on day 15, but did so on day 17 .…”

“…The oxytocin receptor gene is temporally and spatially regulated in the ovine endometrium throughout the oestrous cycle, with receptors first appearing in the luminal epithelium (LE) on day 14 in sheep, increasing to a peak at oestrus (day 0) when receptors also develop on the glandular epithelium and caruncular stroma (Wathes & Hamon 1993, Stevenson et al 1994. In cattle, the initial rise in oxytocin receptors preceding luteolysis is on day 15-17 ( Jenner et al 1991, Mann & Lamming 1994.…”

Relationship between endometrial oxytocin receptors and oxytocin-induced prostaglandin F2 release during the oestrous cycle and early pregnancy in pony mares

“…In these species endometrial oxytocin binding is maximal at the time of oestrus and is downregulated sharply in the luteal phase (cattle: Fuchs et al, 1990;Jenner et al, 1991; sheep: Roberts el al, 1976;Sheldrick and Flint 1985;rabbits: Small et al, 1978). In women, however, endometrial oxytocin receptor concentrations vary during the menstrual cycle in a manner similar to that in mares, although their density is much lower than in mares (Fuchs and Behrens, 1993 …”

<b>Interferon-tau Polymorphisms and Their Potential Functions in Ruminants</b>

“…Oxytocin is produced and stored in the corpus luteum and is released in response to PGF2á stimulation, which then causes subsequent pulses of uterine PGF2á release. The luminal and superficial glandular epithelium are primary sources of PGF2á during luteolysis, and oxytocin acts on these target tissues by binding to its plasma membrane-associated receptor, which is expressed late in diestrus coincident with the initiation of luteolysis (Jenner et al, 1991;Spencer et al, 1995). Figure 1.…”

“…In a pregnant state, oxytocin receptors are not expressed on the luminal and glandular epithelial endometrium at the time of normal luteolysis (Jenner et al, 1991;Spencer et al, 1995), and the magnitude and frequency of PGF2á pulses is greatly diminished, if not totally ablated. In the sheep, IFN-ô controls oxytocin receptor expression indirectly by limiting the expression of estrogen receptors (Spencer et al, 2004).…”