Short-term dynamic characteristics of diuresis during exogenous pressure perturbations with and without arterial baroreflex control

Although body fluid volume control by the kidneys may be classified as a long-term arterial pressure (AP) control system, it does not necessarily follow that the urine flow (UF) response to changes in AP is slow. We quantified the dynamic characteristics of the UF response to short-term AP changes by changing mean AP between 60 mmHg and 100 mmHg every 10 s according to a binary white noise sequence in anesthetized rats (n = 8 animals). In a baro-on trial (the carotid sinus baroreflex was enabled), the UF response represented the combined synergistic effects of pressure diuresis (PD) and neurally mediated antidiuresis (NMA). In a baro-fix trial (the carotid sinus pressure was fixed at 100 mmHg), the UF response mainly reflected the effect of PD. The UF step response was quantified using the sum of two exponential decay functions. The fast and slow components had time constants of 6.5 ± 3.6 s and 102 ± 85 s (means ± SD), respectively, in the baro-on trial. Although the gain of the fast component did not differ between the two trials (0.49 ± 0.21 vs. 0.66 ± 0.22 µL·min-1·kg-1·mmHg-1), the gain of the slow component was greater in the baro-on than in the baro-fix trial (0.51 ± 0.14 vs. 0.09 ± 0.39 µL·min-1·kg-1·mmHg-1, P = 0.023). The magnitude of NMA relative to PD was calculated to be 32.2 ± 29.8%. In conclusion, NMA contributed to the slow component, and its magnitude was approximately one-third of that of the effect of PD.NEW & NOTEWORTHY We quantified short-term dynamic characteristics of the urine flow (UF) response to arterial pressure (AP) changes using white noise analysis. The UF step response approximated the sum of two exponential decay functions with time constants of ∼6.5 s and 102 s. The neurally mediated antidiuretic (NMA) effect contributed to the slow component of the UF step response, with the magnitude of approximately one-third of that of the pressure diuresis (PD) effect.

Urine Excretion, Organ Distribution, and Placental Transfer of 6PPD and 6PPD-Quinone in Mice and Potential Developmental Toxicity through Nuclear Receptor Pathways

The rubber antioxidant 6PPD has gained significant attention due to its highly toxic transformation product, 6PPD-quinone (6PPDQ). Despite their detection in urines of pregnant women, the placental transfer and developmental toxicity of 6PPD and 6PPDQ are unknown. Here, we treated C57Bl/6 mice with 4 mg/kg 6PPD or 6PPDQ to investigate their urine excretion and placental transfer. Female and male mice exhibited sex difference in excretion profiles of 6PPD and 6PPDQ. Urine concentrations of 6PPDQ were one order of magnitude lower than those of 6PPD, suggesting lower excretion and higher bioaccumulation of 6PPDQ. In pregnant mice treated with 6PPD or 6PPDQ from embryonic day 11.5 to 15.5, 6PPDQ showed ∼1.5-8 times higher concentrations than 6PPD in placenta, embryo body, and embryo brain, suggesting higher placental transfer of 6PPDQ. Using in vitro dual-luciferase reporter assays, we revealed that 6PPDQ activated the human retinoic acid receptor α (RARα) and retinoid X receptor α (RXRα) at concentrations as low as 0.3 μM, which was ∼10-fold higher than the concentrations detected in human urines. 6PPD activated the RXRα at concentrations as low as 1.2 μM. These results demonstrate the exposure risks of 6PPD and 6PPDQ during pregnancy and emphasize the need for further toxicological and epidemiological investigations.

[Comparison of in vivo plasma pharmacokinetics and urine excretion of main components in Xihuang Formula in rats with precancerous lesions of breast cancer]

The UPLC-MS/MS was established for the determination of acetyl-11-keto-beta-boswellic acid(AKBA) and β-boswellic acid(β-BA), the main active components of Olibanum and Myrrha extracts in Xihuang Formula, in rat plasma and urine. The effects of compatibility on the pharmacokinetic behaviors of AKBA and β-BA in rats were investigated, and the differences in pharmacokinetic behaviors between healthy rats and rats with precancerous lesions of breast cancer were compared. The results showed that compared with RM-NH and RM-SH groups, the AUC_(0-t) and AUC_(0-∞) of β-BA increased(P<0.05 or P<0.01), T_(max) decreased(P<0.05 or P<0.01), and C_(max) increased(P<0.01) after compatibility. The trends of AKBA and β-BA were the same. Compared with RM-SH group, the T_(max) decreased(P<0.05), C_(max) increased(P<0.01), and the absorption rate increased in the normal group of Xihuang Formula. The results of urinary excretion showed that there was a decreasing trend in the urinary excretion rate and total urinary excretion of β-BA and AKBA after compatibility, but there was no statistical difference. Compared with normal group of Xihuang Formula, the AUC_(0-t) and AUC_(0-∞) of β-BA increased(P<0.05), T_(max) increased(P<0.05), and the clearance rate decreased in the breast precancerous lesion group. AUC_(0-t) and AUC_(0-∞) of AKBA showed an increasing trend, the in vivo retention time was prolonged, and the clearance rate was reduced, but there was no significant difference compared with the normal group. The cumulative urinary excretion and urinary excretion rate of β-BA and AKBA decreased under pathological conditions, indicating that pathological conditions could affect the in vivo process of β-BA and AKBA, and reduce their excretion in the form of prototype drugs, showing different pharmacokine-tic characteristics from normal physiological conditions. In this study, UPLC-MS/MS analysis method was established, which was sui-table for in vivo pharmacokinetic analysis of β-BA and AKBA. This study laid a foundation for the development of new dosage forms of Xihuang Formula.

Developing models to predict feces and urine excretion in Japanese Black fattening steer by multiple regression analysis

The objective of this study was to develop models for predicting the amount of feces and urine excreted by Japanese Black fattening steer using a dataset of 119 digestion trials for a total of 46 animals. Correlation analysis was used to analyze the relationships between feces and urine excretion and feed intake, feed digestibility, and nitrogen balance. Multiple regression analysis was conducted to develop models for predicting the amount of feces and urine excreted using the explanatory variables selected from various animal and dietary parameters based on P-value (<0.10) and variance inflation factor (<3.0). Resultingly, dry matter intake was a primary predictor of feces excreted. The prediction equation for the amount of feces excretion as a function of body weight, dry matter intake, and calculated total digestible nutrients fits the data well (adjusted coefficient of determination [adj R2 ] = 0.519, root mean square error = 1.57). Furthermore, the nitrogen content in the urine was the primary predictor of the urine excretion amount. Thus, the prediction equation for the amount of urine excreted using the nitrogen content in urine yielded a highly accurate model (adj R2  = 0.813, root mean square error = 4.12).

PBK Model-Based Prediction of Intestinal Microbial and Host Metabolism of Zearalenone and Consequences for its Estrogenicity

Scope

The aim of the present study is to develop physiologically‐based kinetic (PBK) models for rat and human that include intestinal microbial and hepatic metabolism of zearalenone (ZEN) in order to predict systemic concentrations of ZEN and to obtain insight in the contribution of metabolism by the intestinal microbiota to the overall metabolism of ZEN.

Methods and Results

In vitro derived kinetic parameters, apparent maximum velocities (V_max) and Michaelis–Menten constants (K_m) for liver and intestinal microbial metabolism of ZEN are included in the PBK models. The models include a sub‐model for the metabolite, α‐zearalenol (α‐ZEL), a metabolite known to be 60‐times more potent as an estrogen than ZEN. Integrating intestinal microbial ZEN metabolism into the PBK models revealed that hepatic metabolism drives the formation of α‐ZEL. Furthermore, the models predicted that at the tolerable daily intake (TDI) of 0.25 µg kg⁻¹ bw the internal concentration of ZEN and α‐ZEL are three‐orders of magnitude below concentrations reported to induce estrogenicity in vitro.

Conclusion

It is concluded that combining kinetic data on liver and intestinal microbial metabolism in a PBK model facilitates a holistic view on the role of the intestinal microbiota in the overall metabolism of the foodborne xenobiotic ZEN and its bioactivation to α‐ZEL.

A reliable and stable method for the determination of foretinib in human plasma by LC-MS/MS: Application to metabolic stability investigation and excretion rate

Foretinib (GSK1363089) is a multiple receptor tyrosine kinases inhibitor. In this study, a reliable, fast liquid chromatography-tandem mass spectrometric method was described for assaying foretinib in plasma, urine, and rat liver microsome samples. Simple extraction procedure by protein preciptation with acetonitrile was implemented for foretinib and brigatinib (internal standard) analysis. Chromatographic resolution of analytes was achieved on C₁₈ column with the help of isocratic mobile phase. The binary mobile phase consisted of 60% ammonium formate (10 mM, pH 4.2) and 40% acetonitrile at a flow rate of 0.25 mL/min. Run time was 3 min, and both foretinib and brigatinib were eluted within 0.74 and 1.95 min; they were detected in positive ion mode utilizing multiple reactions monitoring mode. Linearity of the proposed method ranged from 5 to 500 ng/mL (r²≥ 0.9993) in the human plasma. Lower limit of quantification and detection were 6.0 and 1.8 ng/mL, respectively. Intraday and interday precision and accuracy were 0.16 to 1.67 % and -2.39 to -0.52 %. In vitro half-life and intrinsic clearance were 24.93 min and 6.56 mL/min/kg, respectively. Literature review showed that no previous studies have been proposed for the analytical quantification of foretinib in human plasma or its metabolic stability. The established method was also applied to estimate the rate of foretinib excretion in rat urine. The developed method can be used for foretinib pharmacokinetic applications.

Vesicle-associated Membrane Protein 3 (VAMP3) Mediates Constitutive Trafficking of the Renal Co-transporter NKCC2 in Thick Ascending Limbs: ROLE IN RENAL FUNCTION AND BLOOD PRESSURE

Renal cells of the thick ascending limb (TAL) reabsorb NaCl via the apical Na⁺/K⁺/2Cl^- co-transporter NKCC2. Trafficking of NKCC2 to the apical surface regulates NKCC2-mediated NaCl absorption and blood pressure. The molecular mechanisms by which NKCC2 reaches the apical surface and their role in renal function and maintenance of blood pressure are poorly characterized. Here we report that NKCC2 interacts with the vesicle fusion protein VAMP3, and they co-localize at the TAL apical surface. We observed that silencing VAMP3 in vivo blocks constitutive NKCC2 exocytic delivery, decreasing the amount of NKCC2 at the TAL apical surface. VAMP3 is not required for cAMP-stimulated NKCC2 exocytic delivery. Additionally, genetic deletion of VAMP3 in mice decreased total expression of NKCC2 in the TAL and lowered blood pressure. Consistent with these results, urinary excretion of water and electrolytes was higher in VAMP3 knock-out mice, which produced more diluted urine. We conclude that VAMP3 interacts with NKCC2 and mediates its constitutive exocytic delivery to the apical surface. Additionally, VAMP3 is required for normal NKCC2 expression, renal function, and blood pressure.

Optimized siRNA-PEG conjugates for extended blood circulation and reduced urine excretion in mice

Some of the main concerns with in vivo application of naked small interfering RNA are rapid degradation and urinary excretion resulting in a short plasma half-life. In this study we investigated how conjugation of polyethylene glycol (PEG) with variable chain length affects siRNA pharmacokinetics and biodistribution.

The PEG chains were conjugated to chemically stabilized siRNA at the 5' terminal end of the passenger strand using click chemistry. The siRNA conjugate remained functionally active and showed significantly prolonged circulation in the blood stream after intravenous injection. siRNA conjugated with 20kDa PEG (PEG20k-siRNA) was most persistent, approximately 50% PEG20k-siRNA remained 1h post-injection, while the uncoupled siRNA was rapidly removed >90% at 15min. In vivo fluorescent imaging of the living animal showed increased concentration of siRNA in peripheral tissue and delayed urine excretion when coupled to PEG 20k. Biodistribution studies by northern blotting revealed equal distribution of conjugated siRNA in liver, kidney, spleen and lung without significant degradation 24 h post-injection. Our study demonstrates that PEG conjugated siRNA can be applied as a delivery system to improve siRNA bioavailability in vivo and may potentially increase the efficiency of siRNA in therapeutic applications.