Proteins secreted from the early ovine conceptus block the action of prostaglandin F2 alpha on large luteal cells.
In this study we evaluated whether the early conceptus secretes a factor that blocks the action of prostaglandin (PG) F2 alpha on cultured ovine large luteal cells. PGF2 alpha inhibited progesterone production by lipoprotein-stimulated large luteal cells and this anti-steroidogenic action was blocked in a dose-dependent manner by conceptus proteins secreted from Day 15 embryos. Purified ovine trophoblast protein-1 (oTP-1) did not exhibit the anti-PGF2 alpha activity, but secreted conceptus proteins devoid of oTP-1 did prevent the anti-steroidogenic effects of PGF2 alpha. This activity does not appear to be a nonspecific effect of protein since neither serum albumin nor thyroglobulin, gamma globulin, insulin, LH, secreted ovine endometrial proteins, or heat-inactivated secreted conceptus proteins had this action. After molecular-sizing chromatography we found a high- and a low-molecular weight fraction with luteal protective activity. Neither of the secreted conceptus protein fractions blocked the binding of 3H-PGF2 alpha to large luteal cells. However, conceptus proteins did block the anti-steroidogenic action of phorbol ester and calcium ionophore on large luteal cells, suggesting that secreted conceptus proteins act after activation of the free calcium/protein kinase C intracellular effector pathways. Thus, the early ovine conceptus secretes a luteal protective protein(s) that may be important for maintaining the corpus luteum during early pregnancy; however, the physiologic significance of this luteal protective protein(s) cannot be stated without further investigation.
Wiltbank
M C
MC
Department of Physiology, Colorado State University, Fort Collins 80523.
Wiepz
G J
GJ
Knickerbocker
J J
JJ
Belfiore
C J
CJ
Niswender
G D
GD
D000818:Animals; D000001:Calcimycin / Q000494:pharmacology; D002850:Chromatography, Gel; D015237:Dinoprost / Q000037:antagonists & inhibitors* / Q000378:metabolism; D005260:Female; D006358:Hot Temperature; D007370:Interferon Type I; D008184:Luteal Cells / Q000187:drug effects / Q000378:metabolism*; D008970:Molecular Weight; D011247:Pregnancy; D011257:Pregnancy Proteins / Q000302:isolation & purification / Q000494:pharmacology / Q000502:physiology*; D011374:Progesterone / Q000096:biosynthesis*; D012756:Sheep / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D007370:Interferon Type I; D011257:Pregnancy Proteins; C020947:interferon tau; D000001:Calcimycin; D011374:Progesterone; D015237:Dinoprost; D013755:Tetradecanoylphorbol Acetate