Broad-spectrum and sensitive screening of more than 1000 compounds in equine urine using liquid chromatography/high-resolution mass spectrometry

RATIONALE

To uphold the integrity of horseracing and equestrian sports, it is critical for an equine doping control laboratory to develop a comprehensive screening method to cover a wide range of target substances at the required detection levels in equine urine.

METHODS

The procedure involved the enzymatic hydrolysis of 3 mL urine samples followed by solid-phase extraction using HF Bond Elut C18 cartridge. The resulting extracts were then separated on a C18 reversed-phase column and analyzed using liquid chromatography/high-resolution mass spectrometry (LC/HRMS) in both electrospray ionization positive and negative modes in two separate injections. The analytical data were obtained in full scan and product ion scan (PIS) modes in an 11 min LC run.

RESULTS

The method can detect 1011 compounds (in both positive and negative ion modes). Over 95% of the target compounds have limits of detections (LODs) ≤10 ng/mL, and more than 50% of the LODs are ≤0.5 ng/mL. The lowest LOD can reach down to 0.01 ng/mL. The applicability of the method was demonstrated by the successful detection of prohibited substances in overseas and domestic equine urine samples.

CONCLUSIONS

We have successfully developed a regular screening method for equine urine samples that can detect more than 1000 compounds at sub-ppb levels in both positive and negative ion modes with full scan and PIS using LC/HRMS. Furthermore, this method can theoretically be expanded to accommodate an unlimited number of prohibited substances in full-scan mode.

Total Carbon Dioxide (TCO2) Concentrations in Thoroughbred and Quarter Racehorses in Louisiana

The TCO₂ (total carbon dioxide) test is performed on the blood of racehorses as a means of combatting the practice of administering alkalizing agents. This study evaluated serum TCO₂ concentrations and factors influencing concentration of TCO₂ in Thoroughbred and Quarter Horses. The normality of data were evaluated with a Shapiro-Wilk test. Mann-Whitney tests and Kruskal-Wallis tests were used against different effects. When a fixed effect was detected, Dunn's post-hoc comparisons were performed. The median pre-race serum TCO₂ concentration (32.20 mmol/L (interquartile range (IQR): 30.80-33.50)) was higher than that of post-race samples (26.70 mmol/L (IQR: 24.55-29.25)) (P < .0001). The median TCO₂ concentrations in pre-race samples were different between Thoroughbred (32.40 mmol/L (IQR: 30.90-33.60)) and Quarter Horses (31.30 mmol/L (IQR: 30.00-32.50)) (P < .0001). The median pre-race TCO₂ concentrations were 32.75 (IQR: 31.40-33.90), 31.40 (IQR: 29.80-32.80), 32.50 (IQR: 31.20-33.88), and 31.60 (IQR 30.00-32.70) mmol/L in racehorses at Fair Grounds, Louisiana Downs, Delta Downs, and Evangeline Downs racetracks, respectively (P < .0001). The total serum TCO₂ concentrations in Thoroughbred and Quarter Horse racehorses were affected by seasonal temperature variation (P < .0001). A smaller sample size was available for post-race samples (n = 205) and Quarter Horse pre-race samples (n = 351). The results of this study indicated that the breed, seasonal temperature variation, pre-race or post-race sampling, and track location are strongly correlated to total TCO₂ concentrations. It was not clear whether the statistically significant differences in TCO₂ levels among racetracks in Louisiana were due to location of racetracks and/or seasonal temperature variation.

Total Carbon Dioxide in Adult Standardbred and Thoroughbred Horses

The TCO2 (total carbon dioxide) test is performed on the blood of racehorses as a means of combatting the practice of administering alkalizing agents for the purpose of enhancing performance. The purposes of this review are to present an overview of the factors contributing to TCO2 and to review the literature regarding TCO2 in adult Standardbred and Thoroughbred horses to demonstrate the range of variability of TCO2 in horses. Most of the research published on the topic of TCO2 or bicarbonate measurement in racehorses was accessed and reviewed. PubMed and Google Scholar were the primary search engines used to source the relevant literature. The main physicochemical factors that contribute to changes in TCO2 in horses at rest are changes in strong ions concentration, followed by changes in weak acid (i.e. plasma albumin) concentrations. There is a wide normal distribution of TCO2 in horses ranging from 23 mmol/L to 38 mmol/L. Independent of administration of alkalizing agents, blood TCO2 is affected mainly by feeding, time of day (diurnal variation), season and exercise. There are few studies that have reported hour-by-hour changes in TCO2. Racehorse population studies suffer from lack of validation regarding whether or not a horse was administered an alkalizing agent. It is concluded that the normal range of TCO2 in non-alkalized Standardbred and Thoroughbred horses is significantly wider than has been appreciated, that periods of elevated TCO2 appear to be normal for many horses at rest, and that a TCO2 test alone is not definitive for the purposes of determining of an alkalizing agent has been administered to a horse.

Doping detection in animals: A review of analytical methodologies published from 1990 to 2019

Despite the impressive innate physical abilities of horses, camels, greyhounds, or pigeons, doping agents might be administered to these animals to improve their performance. To control these illegal practices, anti-doping analytical methodologies have been developed. This review compiles the analytical methods that have been published for the detection of prohibited substances administered to animals involved in sports over 30 years. Relevant papers meeting the search criteria that discussed analytical methods aiming to detect and/or quantify doping substances in animal biological matrices published from 1990 to 2019 were considered. A total of 317 studies were included, of which 298 were related to horses, demonstrating significant advances toward the development of doping detection methods for equine sports. However, analytical methods for the detection of doping agents in sports involving other species are lacking. Due to enhanced accuracy and specificity, chromatographic analysis coupled to mass spectrometry detection is preferred over immunoassays. Regarding biological matrices, blood and urine remain the first choice, although alternative biological matrices, such as hair and feces, have been considered. With the increasing number and type of drugs used as doping agents, the analytes addressed in the published papers are diverse. It is very important to continue to detect and quantify these drugs, recognizing those that are most frequently used, in order to punish the abusers, protect animals' health, and ensure a healthier and genuine competition.

The effect of serial administration of bicarbonate on plasma total CO2 concentrations in horses

The administration of alkalinising agents including bicarbonate is of concern to racing authorities because resultant alkalosis may enhance performance and interfere with the detection of drugs in post-race urine. A threshold for total carbon dioxide (TCO₂ ) of 36.0 mmol/L in plasma (with action limit of 37.0 mmol/L) has been set. Serial dosing of sodium bicarbonate has gained popularity in human athletes but has not been studied in horses previously. Sodium bicarbonate (200 g per horse) and 60 g of an electrolyte-vitamin complex was administered in 2-L water via nasogastric intubation to five Standardbred horses for three consecutive days (total dose bicarbonate 0.42 ± 0.02 g/kg). Serial blood samples were taken over Days 1-5, with the final day (5) intended to simulate a 'clear day', and TCO₂ was analysed. Following the first bicarbonate administration, plasma TCO₂ peaked at 6 h (34.8 ± 1.3 mmol/L), returning to baseline by 23 h. On Day 2, four out of the five horses showed a peak greater than 36.0 mmol/L (mean 37.0 ± 2.1 mmol/L). With daily repeated dosing, plasma TCO₂ peaked progressively earlier, and by Day 3, the peak occurred at 2 h and concentrations declined more rapidly. On Days 4 and 5, TCO₂ levels remained low (<32.1 mmol/L on Day 4 and between 27.0-31.2 mmol/L on Day 5). These studies demonstrate that serial dosing of a 'split dose' of sodium bicarbonate on three consecutive days does not result in the accumulation or carry-over of plasma TCO₂ levels beyond the levels observed following a single dose.

The effect of sodium bicarbonate and validation of beckman coulter AU680 analyzers for measuring total carbon dioxide (TCO2) concentrations in horse serum

This study evaluated the usage of Beckman Coulter AU680 analyzers for measurement of TCO 2 in horse serum, and the effect of sodium bicarbonate administrations on serum TCO 2 levels in resting horses. Treatment of horses with sodium bicarbonate did not result in any adverse events. Mean TCO 2 concentration was significantly higher from 1 to 8 h in the sodium bicarbonate-treated horses compared to the untreated controls. Within an hour, administration of sodium bicarbonate increased the TCO 2 level from 31.5 ± -2.5 (SD) to 34.0 ± 2.65 (SD) mmol/L and at 2-8 h post-administration, the TCO 2 level was above the 36 mmol/L cut-off level. In all quality control analysis of Australian standard by Beckman Coulter AU680 analyzer, the instrument slightly over estimated the TCO 2 level but the values were in close agreement with mean TCO 2 level being 38.03 with ± 0.87 mmol/L (SD). Expanded uncertainty was calculated using different levels of confidence interval. Based on 99.5% confidence interval using 0.805% expanded uncertainty using mean measured concentration of 38.05 mmol/L, it was estimated that any race samples TCO 2 level higher than 38.5 mmol/L will be indicative of sodium bicarbonate administration using Beckman Coulter AU680 analyzer in Louisiana.

Cross Validation of HS-GC/MS to Quantify Total Carbon Dioxide in Horse Plasma

The use of alkinizing agents by trainers to counteract the accumulation of lactic acid in racehorses has been well documented. A by-product of this administration is elevated total carbon dioxide (tCO2) concentrations. Most regulatory authorities have set the threshold for tCO2 in plasma at 37 mM. The quantification of tCO2 often presents a challenge to laboratories due to the instrumentation required, which can be expensive to use and maintain. The Beckman DxC 600 (Brea, CA) is currently used in our laboratory for tCO2 quantification. The goal of this research was to determine if another analytical method could be used for this procedure. We report the use of headspace gas chromatography-mass spectrometry (HS-GC/MS) as an acceptable alternative to the use of the Beckman DxC 600. A six-point calibration curve ranging from 10 to 60 mM was analyzed along with controls at 15, 25 and 45 mM. Imprecision was found to be <3% at all concentrations. Inaccuracy was measured at <4% at all concentrations. Measurement of uncertainty was determined using the Simplified GUM approach and was found to be 3% at 99.7% confidence level with eight measurements at a tCO2 concentration of 45 mM. Furthermore, the HS-GC/MS was cross-validated according to international protocols with all parameters being met. During cross validation, a standard at a known concentration was analyzed by both instruments. The average difference using 25 replicates in calculated concentrations was <0.1 mM. Also, plasma samples from four untreated horses were analyzed by both instruments. The difference in calculated concentrations between the two instruments was <0.6 mM for all horses. The results show that the use of HS-GC/MS is an acceptable alternative to the use of the Beckman DxC 600 for the quantification of tCO2 in horse plasma.

Hydroxylation of multi-walled carbon nanotubes: Enhanced biocompatibility through reduction of oxidative stress initiated cell membrane damage, cell cycle arrestment and extrinsic apoptotic pathway

Modification of CNTs with hydroxyl group promotes their applications in biomedical area. However, the impact of hydroxylation on their biocompatibility is far from being completely understood. In this study, we carried out a comprehensive evaluation of hydroxylated multi-walled carbon nanotubes (MWCNTs-OH) on the human normal liver L02 cell line, and compared it with that of pristine multi-walled carbon nanotubes (p-MWCNTs). Results demonstrated that compared with p-MWCNTs, MWCNTs-OH induced significantly lower oxidative stress as indicated by the level of intracellular antioxidant glutathione (GSH), subsequently lead to less cell membrane damage as demonstrated by lactate dehydrogenase (LDH) leakage assay, and showed slightly decreased arrestment of cell cycle distribution at G0/G1. More interestingly, MWCNTs-OH exhibited significantly lower tendency to activate caspase-8, a key molecule involved in the extrinsic apoptotic pathway. All these in vitro results demonstrated that hydroxylation of MWCNTs enhanced their biocompatibility compare with p-MWCNTs.