Food Chem Toxicol. 2016 Nov;97:243-255. doi: 10.1016/j.fct.2016.09.017.

Gender differences in pharmacokinetics and tissue distribution of 3 perfluoroalkyl and polyfluoroalkyl substances in rats

Sook-Jin Kim1, Seo-Hee Heo1, Dong-Seok Lee1, In Gyun Hwang2, Yong-Bok Lee3, Hea-Young Cho1,*

1 College of Pharmacy, CHA University, 335 Pangyo-ro, Bundang-gu, Seongnam-Si, Gyeonggi-Do, 13488, Republic of Korea

2 Food Safety Risk Assessment Division, National Institute of Food & Drug Safety Evaluation, Ministry of Food and Drug Safety, 187 Osongsaengmyeong 2-ro, Osong-eup, Heungdeok-gu, Cheongju-si, Chungcheongbuk-do, 28159, Republic of Korea

3 College of Pharmacy, Chonnam National University, 77 Yongbong-ro, Buk-gu, Gwangju 61186, Republic of Korea

 

Abstract

The aim of this study was to confirm and investigate the gender differences in pharmacokinetic (PK) characteristics and tissue distribution of 3 perfluoroalkyl and polyfluoroalkyl substances (PFASs) consisted of perfluorooctanoic acid (PFOA), perfluorooctanesulfonic acid (PFOS), and perfluorohexane sulfonic acid (PFHxS) in both male and female rats. For this study, a simultaneous determination method of the 3 PFASs in rat plasma and tissues was developed and validated using a UPLC-MS/MS system. The PK parameters after a single oral or intravenous administration of the 3 PFASs in both rats were calculated using WinNonlin® software. The mean half-life of the 3 PFASs in female and male rats was in the range of 0.15–0.19 and 1.6–1.8 days for PFOA, 23.5–24.8 and 26.4–28.7 days for PFOS, and 0.9–1.7 and 20.7–26.9 days for PFHxS, respectively. The 3 PFASs were highly distributed in the liver and kidney. These results suggest that there are gender differences in the PKs for PFOA and PFHxS in rats, whereas the PFOS represented no significant gender differences except the Kp value of liver. The validated simultaneous determination method of the 3 PFASs was also within the accepted criteria of the international guidance.international guidance.

PMID: 27637925

 

Supplement

Perfluoroalkyl and polyfluoroalkyl substances (PFASs) were introduced in 1950s and have been extensively used in various industrial and commercial applications. The two most widely known PFASs are perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS), and perfluorohexane sulfonic acid (PFHxS) is the third most frequently detected in the world. The PFASs are long-chain fatty acid analogs in which the carbon–hydrogen (C–H) bonds are replaced by carbon–fluorine (C–F) bonds. The common chemical property is their solubility in the environmental media, high stability and non-biodegradability due to the strong C–F bonds [1]. Therefore, they are persistent and have been found worldwide in wildlife and the general populations.

In rodents, the PFOA and PFOS were reported to cause neurotoxicity, hepatotoxicity, and reproductive and developmental toxicities in common [2, 3]. The PFHxS is strongly associated with the rate of hysterectomy, menopause, and serum cholesterol levels in humans [4, 5]. The high exposure of 3 PFASs may lead to early menopause, but the underlying mechanism is not known yet [4]. As reported in the toxicity study, PFOA is no longer used in industry and the worldwide production of PFOS was phased out in 2002. Although the production of several PFASs has reduced in the last decade, it has been still detected in wildlife and human populations around the globe [6]. Even though the concentration of these 3 PFASs was low in biological samples such as plasma and tissues from rodents or humans, their long half-lives could indicate the tendency of bioaccumulation, leading to higher body burdens and associated long-term health risks [7].

A few pharmacokinetic studies (PKs) of the 3 PFASs have been previously published. The plasma elimination half-lives of the 3 PFASs were different among species, and those in humans were longer than in the experimental animals. The tissue distribution studies of the 3 PFASs in rodents were mainly tested in the liver and kidney. In case of PFHxS, the tissue distribution except liver in rodents has not been reported up to now. Moreover, the gender difference of the PKs and tissue distributions of PFOA has been reported [8]. The PFHxS also showed a significant gender different PKs and liver concentrations in rats [9]. However, the PFOS didn’t show any gender differences in the PKs in rats, mice, and monkeys [10]. Therefore, the necessities for additional investigation for the tissue distributions of PFOS and PFHxS in female rats have been raised, and a direct confirmatory comparison study for the gender differences in PKs and tissue distribution of 3 PFASs in rats needed to be performed.

For the disposition study of the 3 PFASs, more improved analytical method should be developed for their determination in biological samples. The reported analytical methods were too complicated, expensive, or time-consuming. Therefore, a simple, rapid, and sensitive analytical method for the simultaneous determination of these 3 PFASs in biological matrixes obtained from animals had to be developed.

Thus, we investigated the gender difference in PK characteristics and tissue distribution of the 3 PFASs after a single IV or oral administration of PFOA, PFOS, and PFHxS in rats. In addition, a simultaneous determination method for the quantitation of the 3 PFASs in rat plasma and tissues was developed and validated by ultra-liquid chromatography coupled tandem mass spectrometry (UPLC-MS/MS).

 

Analytical method development and validation

Simultaneous analytical method for 3 PFASs was constructed with mobile phase of 5 mM ammonium acetate in water and methanol, a flow rate of 0.3 mL/min, and Kinetex® 2.6 µm C8 100 Å column (2.1 mm x 100 mm, 2.7 µm particle size), for chromatographic separation. The mass spectrometer was operated with negative electrospray ionization interface using an Acquity UPLC® system coupled to a mass spectrometer (Xevo TQ-S, Waters Corp.). The method validation was performed on according to the international guidance from U.S. Food and Drug Administration. The results showed a satisfactory precision, accuracy, and reproducibility of the acceptable criteria within ±15% for QC samples and ±20% for LLOQ. The extraction recoveries of PFOA, PFOS, and PFHxS in the rat plasma were 92.5 ± 1.8%, 91.0 ± 3.7%, and 95.5 ± 2.9%, respectively, and the recoveries of each internal standard were 99.4 ± 3.3%, 99.8 ± 6.3%, 98.3 ± 4.8% of MPFOA, MPFOS, and MPFHxS, respectively.

 

 

Figure 1. Full scan mass spectra of (A) PFOA, (B) PFOS, and (C) PFHxS. Multiple reaction monitoring (MRM) transitions were used for quantification, which were m/z 413.1→169.0 for PFOA, m/z 499.0→79.9 for PFOS, and m/z 399.0→80.0 for PFHxS.

 

 

 

Figure 2. Representative MRM chromatograms of PFOA, PFOS, and PFHxS in rat plasma. (A) blank rat plasma, (B) rat plasma containing each analyte at an LLOQ of 1 ng/mL and IS (100 ng/mL), (C) rat plasma taken at 1 h after the oral administration of PFOA (1 mg/kg), PFOS (2 mg/kg), and PFHxS (4 mg/kg) in female rats. The selectivity and specificity were confirmed by the representative chromatograms. The retention times of the 3 PFASs were at 3.19 min of PFOA, 3.47 min of PFOS, 2.87 min of PFHxS, 3.19 min of MPFOA, 3.47 min of MPFOS and 2.87 min of MPFHxS, respectively. No significant interferences were observed for the 3 PFASs at their retention times in blank plasma.

 

Pharmacokinetic study

In rats, the AUC0-∞, t1/2, CL, and CLr of PFOA and PFHxS showed a significant gender difference, whereas PFOS represented no significant differences. We investigated the 9 tissues of the heart, lungs, liver, kidneys, spleen, brain, GI tract, muscle, and fat in rats. The 3 PFASs were highly detected in as follows: liver>kidney>lung. The tissue-to-plasma partition coefficient (Kp) values of 3 PFASs in the liver showed a significant gender difference, except for PFHxS.

 

 

Figure 3. Mean tissue concentration at the terminal time (PFOA, 12 day in male, 24 h in female; PFOS, 70 day in male and female; PFHxS, 72 day in male, 14 day in female) after oral or IV administration of (A) PFOA (1 mg/kg), (B) PFOS (2 mg/kg), and (C) PFHxS (4 mg/kg) in male and female rats (mean ± SEM, n = 5). We compared the concentration of 3 PFASs in the 5 organs with faster blood flow, higher Kp value, and toxic sensitivity. The 3 PFASs were highly transferred to the liver and kidney. The Kp values of PFOA and PFOS in the liver showed a significant gender difference, whereas the Kp values of PFHxS were less than 1, and represented no significant differences.

 

 

Figure 4. Mean plasma concentration-time profile of (A) PFOA, (B) PFOS, and (C) PFHxS after IV administration of PFOA (1 mg/kg), PFOS (2 mg/kg), and PFHxS (4 mg/kg) in male (blue circle ) and female (red square) rats (mean ± SEM, n = 5). The model best fitted to one-compartment model for PFOA, and two-compartment model for PFOS and PFHxS. For the PFOA and PFHxS, the PK parameters of the AUC0-∞, t1/2, CL, and CLr showed a significant gender difference (at least 8 times for PFOA, 23 times for PFHxS). The AUC0-∞, t1/2, CL, and CLr of PFOS showed no significant gender differences in rats. The Vd of 3 PFASs did not present any significant gender differences in rats.

 

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