Interferon tau (IFN-τ) is the pregnancy recognition signal secreted by the trophectodermal cells of the developing bovine embryo that prevents luteolysis and maintains critical progesterone production. Recent evidence has suggested in addition to the mechanism of action identified in the uterus, there may be a direct effect of IFN-τ on...
Experiments were conducted to determine whether endogenous progesterone regulates synthesis and/or secretion of luteal oxytocin (OT). In experiment 1, mature ewes (n=5 per group) were assigned randomly to control or mifepristone (RU 486) treatment groups. Ewes were injected twice daily s.c. with vehicle or 10 mg RU 486 from days...
Prostaglandin F₂α (PGF₂α), a stimulatory hormone of luteal oxytocin
secretion, is known to activate protein kinase C (PKC); however, the
intracellular signals that promote exocytosis of oxytocin remain to be
elucidated. Myristoylated alanine-rich C kinase substrate (MARCKS), a
protein specifically phosphorylated by PKC, crosslinks actin filaments
associated with the inner...
To determine whether membrane-related events may be involved in
attenuated luteal function after gonadotropin-releasing hormone (GnRH)
administration, corpora lutea (CL) were removed from 10 beef heifers on day 7
of the estrous cycle after i.v. injection of GnRH or saline on day 2 of the cycle.
Luteal slices were incubated...
Two experiments were conducted to examine the effect of
a cyclopropenoid fatty acid on luteal cell function. In Exp.
1, 12 mature ewes were mated to a fertile ram, assigned to two
groups (n = 6/group) and laparotomized on day 18 of gestation.
Ewes with corpora lutea (CL) in both...
Experiments were conducted to examine the effects of a tumor-promoting phorbol ester, a calcium ionophore and indomethacin on bovine luteal oxytocin (OT) synthesis and secretion and progesterone secretion. Six 18-month-old crossbred beef heifers in Exp. 1 and five similar heifers in Exp. 2 were observed twice daily for estrus using...
Four experiments were conducted to determine oxytocin concen tration of bovine luteal tissue at different stages of the estrous cycle and to study the effects of prostaglandins F₂α (PGF₂α), E₂ (PGE₂), luteinizing hormone (LH), cycloheximide, colchicine and cytochalasin B on oxytocin synthesis and release in vitro. In experiment 1, luteal...