Tandem Mass Spectrometry Method for the Quantification of Serum Busulfan

Busulfan, an alkylating agent, is most commonly used as a component of bone marrow transplantation preoperative regimens. Significant interpatient and intrapatient variations in pharmacokinetics require individualizing the dosage based on area under the time-versus-concentration curve. Timely result reporting is critical to dose adjustment to reduce morbidity and mortality associated with the regimen. The authors developed a rapid, accurate, and sensitive method for the quantification of serum busulfan using direct inject tandem mass spectrometry. Plasma samples (50 microL) are extracted in 1 mL of methanol containing 1,6-bis-(methanesulfonyloxy)hexane as an internal standard. The supernatant is dried under nitrogen (40 degrees C, 30 minutes) and then dissolved in 200 microL methanol and transferred into a clean glass vial suitable for LC/MS/MS analysis. The sample is delivered using an HPLC pump that delivers 0.2 mL of methanol per minute, and 20 microL of sample is injected into a turbo ion spray-equipped tandem mass spectrometer. Total analysis time is 5 minutes. The Q1/Q3 transition for busulfan (BU) is monitored at 269/55 and 297.1/55.1 for the internal standard. The assay is linear to 10 micromol/L and sensitive to at least 0.5 micromol/L. The interassay reproducibility at 1, 2.2, and 4.4 micromol/L were 4.2%, 5.6%, and 6.3%, respectively. Within-run precision using 3 different control samples was 3.9%, 3.9%, and 6.9%. Mean recovery of 4 different BU concentrations spiked into 10 different BU free plasma samples was 98%. Correlation with an established HPLC-UV method revealed a slope of 0.98, an intercept of 0.1, and r = 0.95 (n = 48). No significant interfering substances or ion suppression was identified. This method is a significant improvement over the existing HPLC-UV method for BU determination. The method is highly accurate, reproducible, and requires less specimen, sample preparation, and analysis time.

Overnight responses of the circulating IGF-I system after acute, heavy-resistance exercise

This study evaluated the individual components of the insulin-like growth factor I (IGF-I) system [i.e., total and free IGF-I, insulin-like growth factor binding protein (IGFBP)-2 and -3, and the acid-labile subunit (ALS)] in 10 young, healthy men (age: 22 +/- 1 yr, height: 177 +/- 2 cm, weight: 79 +/- 3 kg, body fat: 11 +/- 1%) overnight for 13 h after two conditions: a resting control (Con) and an acute, heavy-resistance exercise protocol (Ex). The Ex was a high-volume, multiset exercise protocol that alternated between 10- and 5-repetition maximum sets with 90-s rest periods between sets. The Ex was performed from 1500 to 1700; blood was obtained immediately postexercise and sampled throughout the night (every 10 min for the first hour and every hour thereafter) until 0600 the next morning. For the first hour, significant differences (P < or = 0.05) were only observed for IGFBP-3 (Ex: 3,801 > Con: 3,531 ng/ml). For the overnight responses, no differences were observed for total or free IGF-I or IGFBP-3, whereas IGFBP-2 increased (Ex: 561 > Con: 500 ng/ml) and ALS decreased (Ex: 35 < Con: 39 microg/ml) after exercise. The results from this study suggest that the impact that resistance exercise exerts on the circulating IGF-I system is not in the alteration of the amount of IGF-I but rather of the manner in which IGF-I is partitioned among its family of binding proteins. Thus acute, heavy-resistance exercise can lead to alterations in the IGF-I system that can be detected in the systemic circulation.

Cardiovascular effects of endothelin in trout

The cardiovascular effects of endothelin-1 (ET-1) in trout were examined in unanesthetized fish, perfused tissues, and isolated vascular rings. In vivo, a bolus of 500 ng/kg body wt ET-1 transiently lowered arterial (postgill) blood pressure (BP) by nearly 30%; 1,500 ng/kg body wt produced a triphasic, pressor-depressor-pressor, response. Continuous infusion of 0.1, 1, 10, and 30 ng.kg-1.min-1 progressively lowered BP but did not affect heart rate (HR), urine flow, or electrolyte excretion. In the in situ perfused heart ET-1 (10(-11) to 10(-8) M) had no effect on HR or power output. ET-1 produced dose-dependent increases in vascular resistance in the perfused gill, renal-skeletal muscle, and splanchnic circulations, and increased tension, independent of endothelium, in vascular rings from celiacomesenteric (CA) and coronary arteries and anterior cardinal veins (CV). Ventral aortas were refractory to ET-1. In vitro, ET-1 effects were slow in onset and long lasting. External calcium was required for maximal ET-1 responses in gill and CA. ET-1 effects on CA but not CV were partially inhibited by calcium channel blockers, diltiazem, and D 600, and by the guanylate cyclase activators, atrial natriuretic factor, and sodium nitroprusside. [3H]water flux across the perfused gill was stimulated by ET-1 through what appeared to be a vascular-independent mechanism. These experiments show that the trout vasculature is exquisitely sensitive to ET-1, and they suggest that the physiological expression of this peptide has been highly conserved during the course of vertebrate evolution.