https://ogma.newcastle.edu.au/vital/access/ /manager/Index en-au 5 https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:12328 2+ concentration ([Ca²⁺]_i), through enhancing extracellular Ca²⁺ entry and Ca²⁺ release from the sarcoplasmic reticulum, processes that are intimately linked with mitochondria. This study examined the effects of oxytocin on mitochondrial function. This was achieved by measuring the ratiometric JC-1 fluorescence signal in isolated myometrial cells, which provides a relative measure of the mitochondrial membrane potential (ψ_m), and also by loading the cells with Oregon Green BAPTA-AM to examine changes in [Ca²⁺]_i. Oxytocin (1 nm) depolarized the ψ_m to 73.8 ± 3.7% of the control value (P < 0.05; perfused for 11 min) and also caused a transient increase in [Ca²⁺]_i. The depolarization of mitochondrial membrane potential was effectively reversed by 2-aminoethoxydiphenyl borate, nifedipine, Ca²⁺-free solution or oligomycin, with the ratiometric JC-1 fluorescence signal becoming no different from the control value in all cases (i.e. P > 0.05). The reduction in ψ_m is likely to occur at least in part through the oxytocin-induced increase in [Ca²⁺]_i, causing enhanced mitochondrial uptake of Ca²⁺ and resultant dissipation of the mitochondrial electrochemical gradient. ATP synthase is also stimulated, which would further contribute to a decrease in ψ_m.]]> Sat 24 Mar 2018 08:11:37 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:29021 A/B human myometrial cell line, abundance of pSer345-PRA was induced by progesterone in a dose-(EC₅₀ ~1 nM) and time-dependent manner. Prevention of pSer345 (by site-directed mutagenesis) abolished the capacity for PR-A to inhibit anti-inflammatory actions of progesterone mediated by PR-B but had no effect on the transrepressive activity of PR-A at a canonical progesterone response element. Taken together, the data show that human parturition involves the phosphorylation of PR-A at serine-345 in myometrial cells and that this process is ligand dependent and induced by a proinflammatory stimulus. We also found that in myometrial cells, pSer345 activates the capacity for PR-A to inhibit antiinflammatory actions of progesterone mediated by PR-B. Phosphorylation of PR-A at serine-345 may be an important functional link between tissue-level inflammation and PR-A-mediated functional progesterone withdrawal to trigger parturition.]]> Sat 24 Mar 2018 07:31:08 AEDT ]]>