Metformin was performed using the multiple reaction monitoring (MRM) mode, based on parent/product ion transitions 130/71. Compounddependent parameters such as declustering potential, entrance potential, collision energy and cell exit potential were set at 41, 8, 35, and 5 V, respectively. Nitrogen gas flow for collision-induced dissociation and dwell time were kept at 4 (arbitrary value) and 100 ms, respectively. The method used for the quantification of quinidine was adopted from Liu et al29 with minormodifications.27,30 The MRM transitions were 325.2/ 172.1 (transition 1) and 325.2/79.1 (transition 2). Compound-dependent parameters such as declustering potential, entrance potential, collision energy, and cell exit potential were set at 58, 10, 47, and 10 V for transition 1, and at 57, 10, 61.64, and 5.5 V for transition 2, respectively. Nitrogen gas flow for collision-induced dissociation and dwell time were kept at 3 (arbitrary value) and 100 ms, respectively. The method adopted from Chen et al31 with minor modifications27,30 was used for the quantification of atropine.Eugenol The MRM transitions were 290.FGF-8b Protein, Human/Mouse 11/124. Compound-dependent parameters such as declustering potential, entrance potential, collision energy, and cell exit potential were set at 79, 4, 35, and 10 V, respectively. Nitrogen gas flow for collision-induced dissociation and dwell time were kept at 3 (arbitrary value) and 100 ms, respectively. The source-dependent parameters of the mass spectrometer were gas 1 (30 psi); gas 2 (60 psi); curtain gas (10 psi); ion spray voltage (5500 V); and temperature (350 1C) for metformin, quinidine and atropine. The transitions for homatropine were 276.1/142. Homatropine was used as an internal standard (IS) for all the drugs, and the conditions were followed as described in Nirmal et al.Standard and sample preparation The stock concentrations of TEA, metformin, quinidine, and atropine used were 7.84, 7.85, 6.13, and 3.468 mmol/ ml. The stock solution was diluted with 50 methanol containing 0.1 formic acid to reach the required concentrations ranging from low to high. The stock solution (3.63 mmol/ml) of IS was further diluted to reach 1.8 nmol/ml in the extraction solvent containing 70 acetonitrile with 0.1 formic acid. Twenty microliters of AH sample was extracted using 200 ml of extraction solvent, vortexed for 1 min, and subjected to centrifugation.PMID:24275718 The clear supernatant of 100 ml was transferred to 96-well plates and subjected to quantification.Pharmacokinetics and statistical analysis The area under the curve (AUC) of AH concentration upto 2 h (AUC0) was calculated by using the linear trapezoidal rule using standard formulae.32 The results are represented as mean EM. Student’s t-test (unpaired) was used to compare the significance between the control and blocker pre-treated groups using SigmaStat statistical software programme ver.2.0 (Jandel, San Jose, CA, USA).EyeFunctional importance of organic cation transporters in the cornea J Nirmal et alResults Transcorneal penetration of OCT blockers in the absence of substrates The transcorneal penetration shows the maximum concentration of quinidine and atropine reached at 30 min was 1.13.38 and 0.54.06 nmol/ml, respectively, after a single topical application (Figure 1). Based on this observation the blocker pre-treatment time has been fixed as 30 min before the substrate administration.Effect of OCT blockade in the transcorneal penetration of TEA TEA (referred to as control) was admini.