Abstract
Hyperglycaemia has been observed with exposure to organophosphate insecticides. This study was designed to compare the effects of calcium channel blockers, alpha-adrenergic, beta-adrenergic, and muscarinic receptor blockers, and of free radical scavengers on insulin secretion from diazinon-treated islets of Langerhans isolated from the pancreas of rats using standard collagenase digestion, separation by centrifugation, and hand-picking technique. The islets were then cultured in an incubator at 37 degrees C and 5 % CO2. In each experimental set 1 mL of 8 mmol L(-1) glucose plus 125 microg mL(-1) or 625 microg mL(-1) of diazinon were added, except for the control group, which received 8 mmol L(-1) glucose alone. The cultures were then treated with one of the following: 30 micromol L(-1) atropine, 100 micromol L(-1) ACh + 10 micromol L(-1) neostigmine, 0.1 micromol L(-1) propranolol, 2 micromol L(-1) nifedipine, 50 micromol L(-1) phenoxybenzamine, or 10 micromol L(-1) alphatocopherol. In all experiments, diazinon significantly reduced glucose-stimulated insulin secretion at both doses, showing no dose dependency, as the average inhibition for the lower dose was 62.20 % and for the higher dose 64.38 %. Acetylcholine and alpha-tocopherol restored, whereas atropine potentiated diazinon-induced hyposecretion of insulin. Alpha-, beta- and calcium channel blockers did not change diazinon-induced effects. These findings suggest that diazinon affects insulin secretion mainly by disturbing the balance between free radicals and antioxidants in the islets of Langerhans and by inducing toxic stress.
Highlights
Pharmaceutical Sciences Branch, Islamic Azad University, Tehran1; Institute of Medicinal Plants, ACECR, Tehran2; Faculty of Pharmacy, and Pharmaceutical Sciences Research Center, Tehran University of Medical Sciences, Tehran, Iran3
This study was designed to compare the effects of calcium channel blockers, alpha-adrenergic, beta-adrenergic, and muscarinic receptor blockers, and of free radical scavengers on insulin secretion from diazinon-treated islets of Langerhans isolated from the pancreas of rats using standard collagenase digestion, separation by centrifugation, and hand-picking technique
The results of this study have shown that diazinon significantly reduces glucose-stimulated insulin secretion in a manner that is not dose-dependent (62.20 % inhibition at 125 μg mL-1 and 64.38 % at 625 μg mL-1)
Summary
Yl]ethanesulfonic acid (HEPES), collagenase V, NaCl, KCl, MgSO ⋅7H O, Na HPO ⋅12H O, KH2PO4, NaHCO3, glucosexH2O, CaCl2⋅2H2O, NaH PO , MgCl , HCl, bovine serum albumin (BSA), alpha-tocopherol (Trolox®), acetylcholine, neostigmine, and diazinon were purchased from. Batches of 10 islets were treated with one of the following solutions: 30 μmol L-1 atropine, 100 μmol L-1 ACh+10 μmol L-1 neostigmine, 0.1 μmol L-1 propranolol, 2 μmol L-1 nifedipine, 50 μmol L-1 phenoxybenzamine, or 10 μmol L-1 alphatocopherol. The islets were incubated for 30 minutes in a water bath (at 37oC), tubes were placed on ice, and the supernatant was taken to measure secreted insulin using the ELISA method [10].
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