Molecular control of luteal secretion of progesterone

Abstract

The control of progesterone synthesis in the corpus luteum is more complex than is shown in the general pathway for biosynthesis of progesterone in a luteal cell ( Fig. 1) because there are at least two morphologically and biochemically distinct steroidogenic types of cell in the corpus luteum of cattle and sheep and most other mammalian species (Niswender and Nett, 1994; Fig. 2). In ewes, small luteal cells are 12-20 µm in diameter, thought to be of follicular thecal cell origin, contain receptors for LH, respond to LH or cAMP with a 5-15-fold increase in secretion of progesterone, and often contain numerous lipid droplets. Large luteal cells (> 20 µm) are primarily of granulosal cell origin, secrete high basal concentrations of progesterone, and although LH receptors are present, do not respond to LH or cAMP with increased secretion of progesterone. Large cells contain receptors for PGF 2α and respond to this hormone with activation of at least two second messenger pathways. Activation of protein kinase C (PKC) results in decreased secretion of progesterone. Increased concentrations of intracellular free calcium (Wiltbank et al., 1991) resulting from increased binding of PGF 2α to its receptor appear to induce apoptosis and cell death. Steroidogenic luteal cells also contain a broad array of receptors for additional regulatory hormones and factors that may or may not be cell-type specific. Chronic regulation of the secretion of progesteroneIt has been known for some time that LH is critical for normal luteal function in domestic animals (Kaltenbach et al., 1968; Denamur et al., 1973; Hansel et al., 1973). Many of the actions of LH on luteal cells have been elucidated and both acute and long-term effects of LH on luteal steroidogenesis have been demonstrated. Stimulation by LH is critical for the long-term steroidogenic capability of luteal cells, including maintenance of normal amounts of mRNA encoding 3β-hydroxysteroid dehydrogenase/∆ 5 ,∆ 4 isomerase (3β-HSD), cytochrome P450 side chain cleavage enzyme

Impact of contrasting fish oil concentrations in the diet on ovine embryo development <i>in vivo</i> and of corresponding diet-specific derivative sera during <i>in vitro</i> culture

“…However, because fish oil was not the dietary lipid supplement in that instance, the recent reports by Wonnacott et al (2010) and Hughes et al (2011) are more pertinent to the current study. Among their findings, Hughes et al (2011) indicated that n-3 PUFAs specifically enhance progesterone synthesis by thecal cells of ovine follicles and that this is associated with increased StAR transcript expression, notable because the translated steroidogenic acute regulatory protein is an important facilitator of cholesterol transport to mitochondrial membranes, the rate-limiting step in progesterone biosynthesis (Stocco and Clark, 1996;Niswender, 2002). Further reassurance that fish oil was unlikely to have compromised luteal-phase progesterone production in the present study derives from the fact that n-3 fatty acids in fish oil appear able to confer an additional benefit of reducing the synthesis of the uterine antiluteolytic agent, PGF 2α , even when luteal-phase progesterone concentrations are low (Wamsley et al, 2005).…”

The effect of oxytocin on progesterone secretion, phosphoinositide hydrolysis and intracellular mobilisation of Ca 2+ in porcine luteal cells

“…The CL is a primary source of P 4 , a prerequisite hormone required for the maintenance of pregnancy (Niswender, 2002). Inhibition of luteal P 4 production is a key feature of luteolysis occurring in cyclic non-pregnant females.…”

“…An association between activation of the PKC- [Ca 2+ ] i system and luteal secretion of P 4 was observed in pigs (Ciereszko et al, 1998) and ruminants (Niswender, 2002). Oxytocin produced locally in the porcine CL appears to act as a para/autocrine modulator of luteal steroidogenesis (Einspanier et al, 1991;Pitzel et al, 1993bPitzel et al, , 1993c, but no data are available concerning OT signalling in porcine luteal cells.…”

Função do interferon-tau durante o reconhecimento materno da gestação em ruminantes

“…Em bovinos, estudos com CL demonstraram a presença de receptores PTGFR, em células endoteliais e células luteais pequenas, em quantidade pouco significativa, ao contrário das células luteais grandes, nas quais esses receptores são abundantes (SAKAMOTO et al, 1994). Já em ovelhas, o PTGFR foi identificado somente nas células luteais grandes, enquanto que as células luteais pequenas não respondem à ação da PGF2 (NISWENDER, 2002). A resposta luteal à PGF2 é a diminuição da síntese de progesterona, pela diminuição da captação e do transporte de colesterol celular e pela diminuição da expressão de enzimas esteroidogênicas (NISWENDER et al, 2000).…”