The role of intra-luteal factors in the control of the porcine corpus luteum.
In this paper we review three intra-luteal factors and their roles in the corpus luteum (CL). Insulin-like growth factor (IGF)-I, together with its receptor and IGF-binding proteins (IGFBPs), represent an important control system in the CL. IGF-I is a product of small luteal cells and has steroidogenic (i.e. luteotrophic) actions on large luteal cells via the type I receptor, while IGFBPs (e.g. BP-2 and 3; small cells) generally inhibit IGF-Is actions. IGF-I is particularly important in early CL development (up to day 7 of the oestrous cycle) in the pig. Tumour necrosis factor (TNF)-alpha is a product of luteal macrophages that infiltrate CLs in increasing numbers as the cycle progresses. TNF-alpha has been shown to play an important role in luteolysis, but we hypothesise that in the pig, this factor plays an additional role during the mid-luteal phase (days 7-13) in promoting the acquisition of luteal sensitivity to the luteolytic actions of prostaglandin (PG)F2alpha (= luteolytic sensitivity; LS). Endothelin (ET)-1 is a product of (luteal) endothelial cells, and along with its receptors (ETA and ETB) and endothelin-converting enzyme (ECE)-1, represent an intra-luteal system that also plays a role in luteolysis, in association with PGF2alpha. Since TNF-alpha induces endothelial cells to secrete ET-1, we hypothesise that ET-1 mediates the sensitising effects of TNF-alpha on the porcine CL during the mid-luteal phase (days 7-13). Finally, we hypothesise that TNF-alpha and/or ET-1 act to up-regulate luteal protein kinase C (e.g. isoforms betaII and epsilon) activity and thereby sensitises luteal cells to PGF2alpha.
Gadsby
J
J
Department of Molecular Biomedical Sciences, College of Veterinary Medicine, North Carolina State University, Raleigh, NC, USA. John_Gadsby@ncsu.edu
Rose
L
L
Sriperumbudur
R
R
Ge
Z
Z
D000818:Animals; D003338:Corpus Luteum / Q000378:metabolism*; D015237:Dinoprost / Q000378:metabolism; D019332:Endothelin-1 / Q000378:metabolism; D004971:Estrus / Q000378:metabolism*; D005260:Female; D018969:Insulin-Like Growth Factor Binding Proteins / Q000378:metabolism*; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D003341:Luteolysis; D019899:Paracrine Communication / Q000502:physiology; D017526:Receptor, IGF Type 1 / Q000378:metabolism; D013552:Swine / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
D019332:Endothelin-1; D018969:Insulin-Like Growth Factor Binding Proteins; D014409:Tumor Necrosis Factor-alpha; D007334:Insulin-Like Growth Factor I; D015237:Dinoprost; D017526:Receptor, IGF Type 1