TY - JOUR
T1 - Sensitivity of bovine corpora lutea to prostaglandin F(2α) is dependent on progesterone, oxytocin, and prostaglandins
AU - Skarzynski, Dariusz J.
AU - Okuda, Kiyoshi
N1 - Copyright:
Copyright 2007 Elsevier B.V., All rights reserved.
PY - 1999
Y1 - 1999
N2 - Prostaglandin (PG) F(2α) that is released from the uterus is essential for spontaneous luteolysis in cattle. Although PGF(2α) and its analogues are extensively used to synchronize the estrous cycle by inducing luteolysis, corpora lutea (CL) at the early stage of the estrous cycle are resistant to the luteolytic effect of PGF(2α). We examined the sensitivity of bovine CL to PGF(2α) treatment in vitro and determined whether the changes in the response of CL to PGF(2α) are dependent on progesterone (P4), oxytocin (OT), and PGs produced locally. Bovine luteal cells from early (Days 4-5 of the estrous cycle) and mid-cycle CL (Days 8-12 of the estrous cycle) were preexposed for 12 h to a P4 antagonist (onapristone: OP; 10-4 M), an OT antagonist (atosiban: AT; 10-6 M), or indomethacin (INDO; 10-4 M) before stimulation with PGF(2α). Although OP reduced P4 secretion (p < 0.001) only in early CL, it reduced OT secretion in the cells of both phases examined (p < 0.001). OP also reduced PGF(2α) and PGE2 secretion (p < 0.01) from early CL. However, it stimulated PGF(2α) secretion in mid-cycle luteal cells (p < 0.001). AT reduced P4 secretion in early and mid-cycle CL (p < 0.05). Moreover, PGF(2α) secretion was inhibited (p < 0.05) by AT in early CL. The OT secretion and the intracellular level of free Ca2+ ([Ca2+](i)) were measured as indicators of CL sensitivity to PGF(2α). PGF(2α) had no influence on OT secretion, although [Ca2+](i) increased (p < 0.05) in the early CL. However, the effect of PGF(2α) was augmented (p < 0.01) in cells after pretreatment with OP, AT, and INDO in comparison with the controls. In mid-cycle luteal cells, PGF(2α) induced 2-fold increases in OT secretion and [Ca2+](i). However, in contrast to results in early CL, these increases were magnified only by preexposure of the cells to AT (p < 0.05). These results indicate that luteal P4, OT, and PGs are components of an autocrine/paracrine positive feedback cascade in bovine early to mid-cycle CL and may be responsible for the resistance of the early bovine CL to the exogenous PGF(2α) action.
AB - Prostaglandin (PG) F(2α) that is released from the uterus is essential for spontaneous luteolysis in cattle. Although PGF(2α) and its analogues are extensively used to synchronize the estrous cycle by inducing luteolysis, corpora lutea (CL) at the early stage of the estrous cycle are resistant to the luteolytic effect of PGF(2α). We examined the sensitivity of bovine CL to PGF(2α) treatment in vitro and determined whether the changes in the response of CL to PGF(2α) are dependent on progesterone (P4), oxytocin (OT), and PGs produced locally. Bovine luteal cells from early (Days 4-5 of the estrous cycle) and mid-cycle CL (Days 8-12 of the estrous cycle) were preexposed for 12 h to a P4 antagonist (onapristone: OP; 10-4 M), an OT antagonist (atosiban: AT; 10-6 M), or indomethacin (INDO; 10-4 M) before stimulation with PGF(2α). Although OP reduced P4 secretion (p < 0.001) only in early CL, it reduced OT secretion in the cells of both phases examined (p < 0.001). OP also reduced PGF(2α) and PGE2 secretion (p < 0.01) from early CL. However, it stimulated PGF(2α) secretion in mid-cycle luteal cells (p < 0.001). AT reduced P4 secretion in early and mid-cycle CL (p < 0.05). Moreover, PGF(2α) secretion was inhibited (p < 0.05) by AT in early CL. The OT secretion and the intracellular level of free Ca2+ ([Ca2+](i)) were measured as indicators of CL sensitivity to PGF(2α). PGF(2α) had no influence on OT secretion, although [Ca2+](i) increased (p < 0.05) in the early CL. However, the effect of PGF(2α) was augmented (p < 0.01) in cells after pretreatment with OP, AT, and INDO in comparison with the controls. In mid-cycle luteal cells, PGF(2α) induced 2-fold increases in OT secretion and [Ca2+](i). However, in contrast to results in early CL, these increases were magnified only by preexposure of the cells to AT (p < 0.05). These results indicate that luteal P4, OT, and PGs are components of an autocrine/paracrine positive feedback cascade in bovine early to mid-cycle CL and may be responsible for the resistance of the early bovine CL to the exogenous PGF(2α) action.
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U2 - 10.1095/biolreprod60.6.1292
DO - 10.1095/biolreprod60.6.1292
M3 - Article
C2 - 10330083
AN - SCOPUS:0033047361
VL - 60
SP - 1292
EP - 1298
JO - Biology of Reproduction
JF - Biology of Reproduction
SN - 0006-3363
IS - 6
ER -