Effects of streptozotocin-induced diabetes on action potentials
in the sinoatrial node compared with other regions of the rat heart |
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Authors: | F C Howarth R Al-Sharhan A Al-Hammadi M A Qureshi |
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Institution: | (1) Department of Physiology, Faculty of Medicine & Health Sciences, United Arab Emirates University, P.O. Box 17666, Al Ain, Abu Dhabi, UAE |
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Abstract: | In vivo biotelemetry studies have demonstrated that heart rate (HR) is progressively and rapidly reduced after administration
of streptozotocin (STZ) and that the reduction in HR can be partially normalized with insulin replacement. Reductions in HR
have also been reported in isolated perfused heart and superfused right atrial preparations suggesting that intrinsic defects
in the heart are at least partly responsible for the bradycardia. The regional effects of STZ-induced diabetes mellitus (DM)
on action potentials (APs) in the sinoatrial node (SAN), right and left atria and ventricles have been compared in the spontaneously
beating Langendorff perfused rat heart 10–12 weeks after treatment. HR was significantly reduced in STZ-induced diabetic rat
heart (174 ± 9 BPM) compared to controls (241 ± 12 BPM). The duration of AP repolarization at 50% and 70% from peak AP was
significantly prolonged in SAN, right atrium and right ventricle from STZ-induced diabetic rat compared to age-matched controls.
In the SAN AP duration (APD) at 50% and 70% were 51.7 ± 2.2 and 59.5 ± 2.3 ms in diabetic rat heart compared to 45.2 ± 1.7
and 50.0 ± 1.6 ms in controls, respectively. In contrast APD at 50% and 70% were not significantly altered in the left atrium
and left ventricle. Regional defects in the expression and/or electrophysiology of SAN ion channels, and in particular those
involved in AP repolarization, might underlie heart rhythm disturbances in the STZ-induced DM rat. |
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Keywords: | Streptozotocin-induced diabetes Heart rhythm Action potential Sinaotrial node Atria Ventricles |
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