RESUMEN
Human carnitine/organic cation transporter 1 and 2(hOCTN1 and hOCTN2) mediate transport of endogenous and exogenous compounds. The present study aimed to establish cell models with stable expression of hOCTN1 or hOCTN2 to study interactions with compounds and transporters. MDCK cells were transfected with pcDNA3.1(+) plasmid vector containing hOCTN1 or hOCTN2(pcDNA3.1(+)-hOCTN1/2), several stable transfected clones were obtained after G418 screening. hOCTN1 and hOCTN2 clones were screened with ergothioneine and mildronate respectively as substrates to identify the best candidates. We explored interactions of endogenous substances, alkaloids, flavonoids and ACEIs with hOCTN1/2. As a result, the cellular accumulation of ergothioneine in MDCK-hOCTN1 or mildronate in MDCK-hOCTN2 was 122 and 108 folds of the control cells, respectively. The kinetic parameters, Km and Vmax of ergothioneine, mediated by MDCK-hOCTN1, were 8.19±0.61 μmol·L-1 and 1427±49 pmol·mg-1(protein)·min-1; while Km and Vmax of mildronate by MDCKhOCTN2 were 52.3±4.3 μmol·L-1 and 2454±64 pmol·mg-1(protein)·min-1. Dopamine, glutamine, piperine, berberine, nuciferine, lisinopril and fosinopril could inhibit ergothioneine or mildronate uptake by MDCKhOCTN1/2. In conclusion, cell models with good stable hOCTN1 and hOCTN2 functions have been established successfully, which can be applied to the study of interactions between compounds and transporters of hOCTN1 and hOCTN2.
RESUMEN
OBJECTIVE:To establish the method for the determination of mildronate in human plasma and urine,and to study the pharmacokinetic characteristics in healthy volunteers. METHODS:After precipitating plasma and urine sample,LC-MS/MS method was adopted. Dikma Diamonsil C18 column was used with mobile phase consisted of methanol-water(containing 0.2% for-mic acid,0.3% ammonium acetate)(31∶69,V/V)at the flow rate of 0.6 ml/min. ESI was adopted in MRM mode,by using nega-tive ion. The ion for quantitative analysis were m/z 147.10→58.20 (mildronate) and m/z 152.00→110.10 (internal standard,acet-aminophen). The pharmacokinetic parameters of mildronate with single administration and multiple administration were calculated by using DAS 2.1 software and compared. RESULTS:The linear range of mildronate in plasma were 0.02-20 ng/ml(r=0.999 3) and in urine were 0.05-40 ng/ml(r=0.998 2). The lowest limits of quantitation were 0.02 and 0.05 ng/ml. Precision and recovery met the requirements of biological specimen determination,and endogenous impurities hadn’t effect on the determination. The main pharmacokinetics parameters of low-dose,medium-dose and low-dose(250,500,750 mg)of mildronate in plasma with single ad-ministration were as follows:t1/2 were(3.39±0.81),(5.52±0.57)and(5.32±0.96)h;tmax were(0.80±0.45),(1.38±0.43)and (1.10±0.36)h;cmax were(4.17±1.46),(8.08±1.04)and(15.04±1.86)ng/ml;AUC0-36 h were(24.55±5.81),(45.50±7.07)and (85.60 ± 13.09)ng·h/ml. In the dose range,cmax,AUC0-36 h h had a linear relationship with dose (R2 were 0.974 5 and 0.968 3). The main pharmacokinetic parameters of low-dose of mildronate with multiple administration after keeping stable were as follows:cmin was(0.28 ± 0.10)ng/ml;AUCs was(38.78 ± 4.18)ng·h/ml;cs was(1.62 ± 0.17)ng/ml;DF was(3.81 ± 1.14);t1/2 was(6.17 ± 1.46)h;tmax was(1.20 ± 0.33)h;cmax was(6.46 ± 1.96)ng/ml;AUC0-36 h was(40.33 ± 4.65)ng·h/ml;accumulation factor of cmax and AUC were(1.73±0.90)and(1.64±0.40). Compared with single administration,t1/2,cmax and AUC of mildronate with multiple admin-istration after keeping stable all changed,and tmax had no signifi-cant difference. After single administration,26 h accumulative excretion rate of those groups were (0.004 009 ± 0.001 1)%, (0.004 026±0.001 01)% and(0.003 858±0.000 68)% respec-tively. CONCLUSIONS:Established method is sensitive,accurate and specific,and suitable for the determination of mildronate concentration in human plasma and urine and pharmacokinetics study. Mildronate capsule shows certain accumulation effect in healthy volunteers,and linear pharmacokinetic characteristics.