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Objective: To determine thiopurine S-methyltransferase (TPMT) activity and the range of TPMT activity values for the Indian population. Methods: An isocratic reversed-phase high-performance liquid chromatography method with ultraviolet detection for the determination of TPMT activity in red blood cells was developed and validated. TPMT activity (nmol of 6-methylmercaptopurine [6-MMP]/h/ml erythrocytes) was measured based on the conversion of 6-mercaptopurine to 6-MMP with S-adenosyl-l-methionine. The stability of erythrocyte lysate at −20°C and the whole-blood specimens for TPMT activity were determined at 4°C. TPMT enzyme activity was measured in 150 patients who were not on azathioprine (AZA), and population difference in TPMT enzyme activity was evaluated. Results: The assay was linear from 1.0 to 60.14 nmol 6-MMP concentrations. The chromatogram peaks obtained were baseline separated for 6-MMP and the internal standard. The bias and precision of low-, medium-, and high-quality controls (QC) were within acceptable limits. Stock and lysate specimens were found to be stable in −20°C. The Indian populations have a considerable number of patients with low- and intermediate-TPMT activity. The wide range of TPMT activity in the study population (3.85–35.68 nmol/h/ml erythrocytes) is suggestive of high inter-individual variability in the formation of 6-thioguanine nucleotide formation, and therefore clinical efficacy and safety of AZA. Conclusion: A simple isocratic method was developed and validated for measuring TPMT activity in erythrocytes. Measuring TPMT activity before initiating AZA may help to decide the initial dose of AZA in patient management.

A robust and economical assay for routine determination of indocyanine green pharmacokinetics was developed and validated using high-performance liquid chromatography with a photodiode array detector. Plasma specimens from critically ill patients and those with hepatitis on various co-medications were used as blanks for validation of this assay. Extraction of indocyanine green was performed by simple protein precipitation with acetonitrile, and the supernatant was separated using an octadecyl column with detection at 784 nm. Blanks were found to have no interference for 40 blanks of patients who were on 56 different medications. The precision for LLOQ (0.5 µg/ml) as determined by the percentage coefficient of variation was 1.19. Stability of plasma calibration standards and stock were determined over a period of 61 days, and ICG was found to be stable for 20 days. Stability of whole blood specimens containing ICG was determined at 4°C for a period of 4 hours.

Context: Kv7 potassium channels are expressed in several types of smooth muscles and could mediate physiological responses in the tissues expressed. Flupirtine is an analgesic that acts by opening Kv7 potassium channels. It has been shown to inhibit the contractility of several types of isolated smooth muscle. Aims: This study investigated the ability of flupirtine to inhibit the spontaneous contractility of isolated distal caprine (goat) ureter. Settings and Design: Spontaneous contractility of the isolated goat ureter was recorded using a physiograph. Materials and Methods: The ability of 1, 3, 10, 30, and 90 μM concentrations of flupirtine maleate to inhibit the spontaneous contractility of isolated distal goat ureter was investigated. The ability of the nonspecific potassium channel blocker 4-aminopyridine (4-AP; 1 mM) and the specific Kv7 channel blocker XE-991 (100 μM) to reverse the inhibitory effect of flupirtine on ureteric contractility was also investigated. Statistical Analysis Used: Both parametric and nonparametric statistical tests were used. Results: At 10, 30, and 90 μM concentrations, flupirtine significantly inhibited the spontaneous contractility of the isolated goat ureter. The EC50 of flupirtine for a contact period of 10 min was 17.7 μM. The inhibitory effect of flupirtine on ureteric contractility was significantly reversed by 4-AP and XE-991. Conclusions: Flupirtine inhibits the spontaneous contractility of the isolated goat ureter by opening Kv7 channels.

Context: Benidipine is a calcium channel blocker that blocks all the major types (L, N, and T) of calcium channels. It has been shown to inhibit the contractility of many isolated smooth muscles but not isolated ureter. Aims: This study evaluated the ability of benidipine to inhibit the spontaneous contractility of isolated proximal and distal caprine (goat) ureter. Settings and Design: Spontaneous contractility of isolated goat ureter was recorded using a physiograph. Materials and Methods: Benidipine at concentrations in the range of 1 nM to 10 μM was analyzed for its inhibitory effects on the spontaneous contractility of the isolated proximal and distal caprine ureter. Statistical Analysis Used: Both parametric and nonparametric statistical tests were used. Results: The EC50 of benidipine for inhibiting contractility in the distal ureter was found to be 54.68 nM. Benidipine was found to have a greater inhibitory effect on the distal ureter than on the proximal ureter. It was also found to inhibit amplitude of spontaneous ureteric contractility more readily than the frequency of spontaneous ureteric contractility. Conclusions: These results suggest that benidipine has differential inhibitory effects on the spontaneous contractility of the isolated ureter. Benidipine could be useful in the management of clinical conditions like ureteric colic due to its inhibitory effects on the contractility of the ureter.

Lipoprotein-Associated Phospholipase A2 (Lp-PLA2) is a 45-kDa protein of 441 amino acids encoded by the pla2g7 gene in the humans. In the blood it is associated mainly with Low Density Lipoprotein (LDL) and less than 20% is associated with High Density Lipoprotein (HDL). This enzyme is characterized by its ability to specifically hydrolyze PAF as well as glycerophospholipids containing short, truncated, and/or oxidized fatty acyl groups at the sn-2 position of the glycerol backbone. Genetic studies conducted in humans harboring an inactivating mutation at this locus suggest that loss of Lp-PLA2 function is a risk factor for inflammatory and vascular conditions. Consistently, overexpression of Lp-PLA2 has anti-inflammatory or pro-inflammatory actions and anti-atherogenic properties in animal models. This article discusses two simple techniques to estimate Lp-PLA2 activity. New therapeutic agents inhibiting the activity of Lp-PLA2 are being investigated for curative purpose.