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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. [ABSTRACT FROM AUTHOR]

New Psychoactive Substances (NPSs) are defined as a group of substances produced from molecular modifications of traditional drugs. These molecules represent a public health problem since information about their metabolites and toxicity is poorly understood. N-ethyl pentedrone (NEP) is an NPS that was identified in the illicit market for the first time in the mid-2010s, with four intoxication cases later described in the literature. This study aims to evaluate the metabolic stability of NEP as well as to identify its metabolites using three liver microsomes models. To investigate metabolic stability, NEP was incubated with rat (RLM), mouse (MLM) and human (HLM) liver microsomes and its concentration over time evaluated by liquid chromatography–mass spectrometry. For metabolite identification, the same procedure was employed, but the samples were analyzed by liquid chromatography–high resolution mass spectrometry. Different metabolism profiles were observed depending on the model employed and kinetic parameters were determined. The in vitro NEP elimination half-lives (t1/2) were 12.1, 187 and 770 min for the rat, mouse and human models, respectively. Additionally, in vitro intrinsic clearances (Cl int, in vitro) were 229 for rat, 14.8 for mouse, and 3.6 μL/min/mg in the human model, and in vivo intrinsic clearances (Cl int, in vivo) 128, 58.3, and 3.7 mL/min/kg, respectively. The HLM model had the lowest rate of metabolism when compared to RLM and MLM. Also, twelve NEP metabolites were identified from all models, but at different rates of production. [ABSTRACT FROM AUTHOR]

This study predicted dapaconazole clinical drug–drug interactions (DDIs) over the main Cytochrome P450 (CYP) isoenzymes using static (in vitro to in vivo extrapolation equation, IVIVE) and dynamic (PBPK model) approaches. The in vitro inhibition of main CYP450 isoenzymes by dapaconazole in a human liver microsome incubation medium was evaluated. A dapaconazole PBPK model (Simcyp version 20) in dogs was developed and qualified using observed data and was scaled up for humans. Static and dynamic models to predict DDIs following current FDA guidelines were applied. The in vitro dapaconazole inhibition was observed for all isoforms investigated, including CYP1A2 (IC50 of 3.68 µM), CYP2A6 (20.7 µM), 2C8 (104.1 µM), 2C9 (0.22 µM), 2C19 (0.05 µM), 2D6 (0.87 µM), and 3A4 (0.008–0.03 µM). The dynamic (PBPK) and static DDI mechanistic model-based analyses suggest that dapaconazole is a weak inhibitor (AUCR > 1.25 and <2) of CYP1A2 and CYP2C9, a moderate inhibitor (AUCR > 2 and <5) of CYP2C8 and CYP2D6, and a strong inhibitor (AUCR ≥ 5) of CYP2C19 and CYP3A, considering a clinical scenario. The results presented may be a useful guide for future in vivo and clinical dapaconazole studies. [ABSTRACT FROM AUTHOR]