Abstract：
Multidrug resistance proteins type 4 (MRP4) and 5 (MRP5) play pivotal roles in the transport of cyclic nucleotides in various tissues. However, their specific functions within the lower urinary tract remain relatively unexplored. This study aimed to investigate the effect of pharmacological inhibition of MRPs on cyclic nucleotide signaling in isolated pig bladder. The relaxation responses of the bladder were assessed in the presence of the MRP inhibitor, MK571. The temporal changes in intra- and extracellular levels of cAMP and cGMP in stimulated tissues were determined by mass spectrometry. The gene (ABCC4) and protein (MRP4) expression were also determined. MK571 administration resulted in a modest relaxation effect of approximately 26% in carbachol-precontracted bladders. The relaxation induced by phosphodiesterase inhibitors such as cilostazol, tadalafil, and sildenafil was significantly potentiated in the presence of MK571. In contrast, no significant potentiation was observed in the relaxation induced by substances elevating cAMP levels or stimulators of soluble guanylate cyclase. Following forskolin stimulation, both intracellular and extracellular cAMP concentrations increased by approximately 15.8-fold and 12-fold, respectively. Similarly, stimulation with tadalafil + BAY 41-2272 resulted in roughly 8.2-fold and 3.4-fold increases in intracellular and extracellular cGMP concentrations, respectively. The presence of MK571 reduced only the extracellular levels of cGMP. This study reveals the presence and function of MRP4 transporters within the porcine bladder and paves the way for future research exploring the role of this transporter in both underactive and overactive bladder disorders.NEW & NOTEWORTHY This study investigates the impact of pharmacological inhibition of MRP4 and MRP5 transporters on cyclic nucleotide signaling in isolated pig bladders. MK571 administration led to modest relaxation, with enhanced effects observed in the presence of phosphodiesterase inhibitors. However, substances elevating cAMP levels remained unaffected. MK571 selectively reduced extracellular cGMP levels. These findings shed light on the role of MRP4 transporters in the porcine bladder, opening avenues for further research into bladder disorders.
摘要：
多药耐药蛋白4型（MRP4）和5型（MRP5）在各种组织中环核苷酸的转运中起关键作用。然而,它们在下尿路内的特定功能仍未被探索。本研究旨在探讨药物抑制MRPs对离体猪膀胱环核苷酸信号的影响。在存在MRP抑制剂的情况下评估膀胱的松弛反应，MK571.通过质谱法测定受刺激组织中cAMP和cGMP的细胞内和细胞外水平的时间变化。还测定了基因(ABCC4)和蛋白质(MRP4)的表达。MK571给药在卡巴胆碱预收缩膀胱中产生约26%的适度松弛效应。磷酸二酯酶抑制剂如西洛他唑诱导的松弛，他达拉非,在MK571存在下，西地那非显着增强。相比之下,在升高cAMP水平的物质或可溶性鸟苷酸环化酶刺激剂诱导的松弛中未观察到显着的增强作用。在毛喉素刺激后，细胞内和细胞外cAMP浓度增加了约15.8倍和12倍，分别。同样，他达拉非+BAY41-2272刺激导致细胞内和细胞外cGMP浓度增加约8.2倍和3.4倍，分别。MK571的存在仅降低了cGMP的细胞外水平。这项研究揭示了猪膀胱内MRP4转运蛋白的存在和功能，并为未来研究探索该转运蛋白在活动不足和活动过度膀胱疾病中的作用铺平了道路。
