Progesterone Stimulation by LH Involves the Phospholipase-C Pathway in Bovine Luteal Cells

Abstract.We studied the secretory function of the corpus luteum (CL) in cows following different estrus synchronization protocols. Estrus was synchronized using one (n=4) or two injections (n=5) of prostaglandin F2α (PGF2α; dinoprost), two injections of different analogues of PGF2α (aPGF2α), luprostiol (n=5) and cloprostenol (n=5), at eleven-day intervals, a gestagen implant (norgestomet, n=5, for 10 days) or norgestomet together with a subsequent dinoprost injection on the day of implant removal (n=5). CL samples were collected by ovariectomy on Day 7-8 of the estrous cycle. Luteal strips were stimulated with LH (100 ng/ml) or prostaglandin E2 (PGE2, 10 -6 M) for 24 h in culture media. The progesterone (P4) and PGE2 concentrations in the media were measured by enzyme immunoassay. In the control CL (spontaneous estrus; n=5), LH and PGE2 stimulated P4 and PGE2 (P<0.001). The effects of both factors on P4 were reduced in the CL following dinoprost-and cloprostenol-synchronized estrus (P<0.05) and were absent in the luprostiol-synchronized CL (P>0.05). In the norgestomet-synchronized CL, the stimulatory effects of LH and PGE2 were higher compared with the CL synchronized by aPGF2α (P<0.05). Pharmacological manipulation of the estrous cycle using aPGF2α may cause lower P4 secretion. Estrus synchronization inhibited CL sensitivity to luteotropic factors. Therefore, attention should be focused on the estrous synchronization method in both in vivo and in vitro studies of CL functions in cattle. Key words: Cattle, Corpus luteum (CL), Estrus synchronization, Progesterone, Prostaglandin E2 (PGE2), Prostaglandin F2α (PGF2α) analogue (J. Reprod. Dev. 55: [170][171][172][173][174][175][176] 2009) he physiological processes of corpus luteum (CL) formation, growth and maintenance might be regulated by many different factors including luteinizing hormone (LH) and prostaglandin (PG)s [1,2]. After ovulation, as the CL forms from the wall of the ruptured follicle, it grows and rapidly vascularizes [3]. The CL is a complex tissue composed of parenchymal (steroidogenic) and nonparenchymal (fibroblast, vascular smooth muscle, pericyte and endothelial) cells [3,4]. Disturbances in physiological conditions and pharmacological manipulations during follicle growth and maturation, ovulation and as well during early CL formation influence the future secretory function of this new formed endocrine gland.The main function of the CL is secretion of progesterone (P4), an important hormone for the establishment and maintenance of a successful pregnancy [1,2,5]. In domestic animals, LH, which is released in a pulsatile fashion from the anterior pituitary, is one of the most potent regulators of P4 production [6]. LH stimulates basal P4 production in small luteal cells via the LH receptor. In addition to pituitary LH, intraluteal substances produced by the component cells of the CL play important roles in regulating P4 production during the luteal stages and pregnancy [1,2,7]. Arachidonic acid metabolites, such as PGE2 and PGI2, have been prop...

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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In Vitro Assessment of Progesterone and Prostaglandin E2 Production by the Corpus Luteum in Cattle Following Pharmacological Synchronization of Estrus

Skarzynski

Siemieniuch

Pilawski

et al. 2009

“…Among these substances, luteinizing hormone (LH) [21,22], epidermal growth factor (EGF) [23], and prostaglandin (PG) E2 [24,25] have been reported to stimulate accumulation of cAMP via activation of adenylate cyclase (AC), whereas PGF2α is known to activate PKC in luteal cells [15,26]. Therefore, it is possible that substances that activate AC or PKC, such as LH, EGF, PGE2, and PGF2α may act as survival factors and protect the bovine CL against apoptosis.…”

Section: Discussionmentioning

confidence: 99%

Possible Roles of Intracellular Cyclic AMP, Protein Kinase C and Calcium Ion in the Apoptotic Signaling Pathway in Bovine Luteal Cells

Tatsukawa

Bowolaksono

Nishimura

et al. 2006

Self Cite

Abstract. Structural luteolysis occurs by apoptosis of luteal cells. The present study examined the effects of activators of well-characterized second messengers on Fas and caspase-3 mRNA expression and on P4 production in luteal cells in order to trace the pro-and anti-apoptotic factors in the bovine corpus luteum (CL). Cultured bovine mid luteal cells were treated for 24 h with a cyclic AMP analogue (8-bromo cyclic AMP; 8br-cAMP; 2.5 mM), a protein kinase C (PKC) activator (phorbol 12-myristate 13-acetate; PMA; 10 µM), or calcium ionophore (A23187; 10 µM). Fas and caspase-3 mRNA expression was inhibited by 8br-cAMP and PMA but was increased by A23187 (P<0.05). In addition, P4 production by bovine luteal cells was stimulated by 8br-cAMP and PMA, whereas it was inhibited by A23187, compared with untreated controls (P<0.05). The overall results suggest that cAMP and PKC suppress apoptosis in bovine luteal cells through inhibition of Fas and caspase-3 mRNA expression and through stimulation of P4 production. Therefore, substances that activate cAMP or PKC may act as survival factors in the bovine CL. Furthermore, substances that mobilize Ca 2+ may act as apoptotic factors by stimulating Fas and caspase-3 expression in the bovine luteal cells.

“…Luteinizing hormone (LH) secreted by the anterior pituitary is the main regulator of luteal function. LH acts through its specific cell surface receptor (LHCGR) and stimulates P 4 production by the CL in ewes [11], rats, sows [12], cows [13] and mares [14]. Steroidogenic acute regulatory protein (StAR) transfers cholesterol from the outer to inner mitochondrial membrane, allowing enzymatic cleavage of the side chain of cholesterol to pregnenolone by P450 cholesterol side-chain cleavage (P450scc).…”

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confidence: 99%

Seasonal Changes in Luteal Progesterone Concentration and mRNA Expressions of Progesterone Synthesis-related Proteins in the Corpus Luteum of Mares

Kozai

Hojo

Takahashi

et al. 2012

Self Cite

Abstract. Although circulating progesterone (P 4 ) levels tend to change with the season, little is known about the seasonal changes of P 4 synthesis-related proteins in the corpus luteum (CL) of mares. To examine these changes, seventy-four ovaries containing a CL were collected from Anglo-Norman mares at a local abattoir in Kumamoto, Japan (~N32°), five times during one year. The stages of the CLs were classified as early, mid and regressed by macroscopic observation of the CL and follicles. The mid CL, which had the highest P 4 concentration, was used to evaluate the seasonal changes in P 4 synthesis. The luteal P 4 concentration and mRNA expression of luteinizing hormone receptor (LHCGR) were lowest during early winter and highest during late winter. The mRNA expressions of steroidogenic acute regulatory protein (StAR), P450 cholesterol side-chain cleavage enzyme (P450scc) and 3β-hydroxysteroid dehydrogenase/Δ5-Δ4 isomerase (3β-HSD) were lowest during early winter and increased during late winter. These results suggest that P 4 synthesis in the CL is affected by the seasonal changes in the mRNA expressions of P 4 synthesis-related proteins in mares. Key words: Corpus luteum, Mares, Progesterone, Reproductive seasonality, Steroidogenesis (J. Reprod. Dev. 58: [393][394][395][396][397] 2012) M ares are seasonal breeders in which day length (DL) is one of the main environmental factors controlling reproductive seasonality [1][2][3]. The reproductive activity of mares reaches a peak during summer, then decreases during autumn and eventually stops through winter as DL decreases. January 1 in the Northern Hemisphere and August 1 in the Southern Hemisphere are used as the official birth dates for many breeds, especially for racing breeds [4]; therefore, the exposure of mares to artificial light has been used to hasten the reproductive season. Thus, studying reproductive seasonality in mares is relevant for the equine industry.In mammals, the corpus luteum (CL) is an endocrine organ producing progesterone (P 4 ), which is essential for the establishment and maintenance of pregnancy. Although several studies have examined seasonal changes in circulating P 4 concentration in mares, the reported results are not consistent, i.e., the circulating P 4 concentration has been reported to decrease [5][6][7], increase [8] or remain unchanged [9] from the breeding to non-breeding season. Therefore, the effects of season on P 4 synthesis in the CL of mares remain unclear.Luteal P 4 production is regulated by several P 4 synthesis-related proteins [10]. Luteinizing hormone (LH) secreted by the anterior pituitary is the main regulator of luteal function. LH acts through its specific cell surface receptor (LHCGR) and stimulates P 4 production by the CL in ewes [11], rats, sows [12], cows [13] and mares [14]. Steroidogenic acute regulatory protein (StAR) transfers cholesterol from the outer to inner mitochondrial membrane, allowing enzymatic cleavage of the side chain of cholesterol to pregnenolone by P450 cholesterol side-chain ...