Animal research methods of the cardiovascular system
Diabetes induction:
Efforts to characterize diabetic conditions and develop novel preventive and therapeutic approaches require animal models such as the non-obese diabetic (NOD) mouse which are genetically predisposed to develop diabetes, or alternatively induction of diabetes in previously healthy animals. A summary of diabetes induction approaches is described below:
Type I. diabetes (insulin-dependent diabetes mellitus/IDDM) induction: Streptozotocin-induced IDDM is a commonly used approach using Streptozotocin a naturally occurring glucosamine-nitrosourea compound induces activation of poly ADP-ribosylation (PARP), an activity particularly toxic to the insulin-producing beta cells of the pancreas in mammals. This toxicity makes the compound useful for treating beta cell-derived cancers – and it also ablates these cells, leaving the animals dependent on exogenously administered insulin. The dosage of this drug required to induce Type 1 diabetes is in the range of 40-120mg/kg ip or iv. Type 2 diabetes may be induced with multiple low doses (Thirunavukkarasu 2007).
Type II. diabetes (metabolic syndrome) induction: This form of the disease is frequently studied using the Zucker Diabetic Fatty (ZDF) and GK rat models, along with transgenic and knock-out mouse strains (Lekli 2007).
Assay for serum cholesterol, triglyceride, LDL and HDL. Serum cholesterol levels in the venous blood of each animal can be measured using a CardioCheck serum cholesterol analyzer (Point Of Care Diagnostics, Ltd., Artarmon, New South Wales, Australia) at time-points 0 (baseline), 4, 8, 12, 32, 40 weeks following initiation of feeding. Additional indicators of cardiovascular health are routinely measured using enzyme-linked immunoassay (ELISA) kits and automated analysis systems. In the Tosaki’s Laboratory at University of Debrecen, the developed kit reagents are typically assayed for plasma or serum levels of each analyte, using a Biotek ELX 808 Microplate Reader. Results are reported in quantity of selected analyte per unit volume of plasma as median values of each of 4 ELISA outcomes (quadruplicates) within a designated interquartile range (IR). In addition to the components listed above, routine analysis of blood is also conducted for glucose, leptin, insulin, aspartate transaminase (AST), Alanine transaminase (ALT), lactate dehydrogenase (LDH or LD), Creatine kinase (CK), ApoA and ApoB (Juhasz 2013, Kertesz 2013).
Electrocardiography (ECG or EKG) measurements. ECG monitoring in our Laboratory is often conducted using the Einthoven’s triangle method, which is fast, cheap and reliably reproducible. This technique involves placement of a triangular formation of three limb leads formed by the two arms and the pubis. The shape forms an inverted equilateral triangle with the heart at the center that produces zero potential when the voltages are summed. It is named after its inventor, Willem Einthoven.
In the case of echocardiography the ECG is leaded by the tableholder (there are four gold strike).
Blood pressure measurements. Assessment of this valuable indicator of cardiovascular status may be consisted using either invasive or non-invasive methodology. These approaches are summarized below:
Invasive Blood Pressure measurement: Direct blood pressure measurement, an invasive surgical procedure, is considered a “gold standard” for comparisons for accuracy with non-invasive blood pressure assessment approaches. Direct blood pressure is best obtained using a rodent’s carotid artery.
Non-invasive blood pressure measurement. In this approach, a cuff is placed on the animal’s tail to occlude the blood flow. Upon deflation, one of several types of non-invasive blood pressure sensors, placed distal to the occlusion cuff, which may be used to monitor the blood pressure. There are three types of non-invasive blood pressure sensor technologies: photoplethysmography, piezoplethysmography and Volume Pressure Recording. Each method uses an occlusion tail-cuff as part of the procedure.