The natural history of the disease of the dilated strain Bio TO-2 of cardiomyopathic hamsters (CMH) is not totally characterized. We investigated its hemodynamic and histomorphometric characteristics at 140, 180, 220, 260, and 300 days of age. Forty CMH and 40 controls were investigated (8 at each stage). Mean arterial pressure (MAP, carotid artery catheter) and cardiac output and femoral blood flow (CO, FBF, transit time method) were measured in anesthetized animals. Systemic (SVR) and femoral (FVR) vascular resistances were calculated. Atria, left and right ventricles (LV, RV), lungs, and liver were weighed. LV cavity area, LV and RV wall thicknesses and collagen densities were determined (computer-assisted image analyzer). Pulmonary and hepatic congestion were assessed (arbitrary scales). Compared with controls, MAP, CO and FBF were significantly lower in CMH throughout the study (on average: -22%, -34%, -33%, respectively), FVR was significantly increased (+15%), but SVR was not significantly modified. Concerning histomorphometric characteristics, differences between groups significantly increased with age for most variables: at 300 days, atria (+292%), RV (+13%), lungs (+44%), and liver (+23%) weights, LV cavity area (+130%), LV (+364%) and RV (+181%) collagen densities were significantly increased in CMH vs controls, whereas LV (-40%) and RV (-23%) wall thicknesses were significantly decreased. At 260 and 300 days, CMH showed significant pulmonary congestion without hepatic alteration. Bio TO-2 CMH progressively develop an alteration of cardiac function leading to decreased MAP and musculo-cutaneous blood flow associated with cardiac remodeling including atria hypertrophy and LV dilation, wall thinning and a rise in collagen density.

Safety Pharmacology studies for the cardiovascular risk assessment, as described in the ICH S7A and S7B guidelines, appear as being far from sufficient. The fact that almost all medicines withdrawn from the market because of life-threatening tachyarrhythmias (torsades-de-pointes) were shown as hERG blockers and QT interval delayers led the authorities to focus mainly on these markers. However, other surrogate biomarkers, e.g., TRIaD (triangulation, reverse-use-dependence, instability and dispersion of ventricular repolarization), have been identified to more accurately estimate the drug-related torsadogenic risk. In addition, more attention should be paid to other arrhythmias, not related to long QT and nevertheless severe and/or not self-extinguishing, e.g., atrial or ventricular fibrillation, resulting from altered electrical conduction or heterogeneous shortening of cardiac repolarization. Moreover, despite numerous clinical cases of drug-induced pulmonary hypertension, orthostatic hypotension, or heart valvular failure, few safety investigations are still conducted on drug interaction with cardiac and regional hemodynamics other than changes in aortic blood pressure evaluated in conscious large animals during the core battery mandatory studies. This critical review aims at discussing the usefulness, relevance, advantages, and limitations of some preclinical in vivo, in vitro, and in silico models, with high predictive values and currently used in supplemental safety studies.

The natural history of the disease of the dilated strain Bio TO-2 of cardiomyopathic hamsters (CMH) is not totally characterized. We investigated its hemodynamic and histomorphometric characteristics at 140, 180, 220, 260, and 300 days of age. Forty CMH and 40 controls were investigated (8 at each stage). Mean arterial pressure (MAP, carotid artery catheter) and cardiac output and femoral blood flow (CO, FBF, transit time method) were measured in anesthetized animals. Systemic (SVR) and femoral (FVR) vascular resistances were calculated. Atria, left and right ventricles (LV, RV), lungs, and liver were weighed. LV cavity area, LV and RV wall thicknesses and collagen densities were determined (computer-assisted image analyzer). Pulmonary and hepatic congestion were assessed (arbitrary scales). Compared with controls, MAP, CO and FBF were significantly lower in CMH throughout the study (on average: -22%, -34%, -33%, respectively), FVR was significantly increased (+15%), but SVR was not significantly modified. Concerning histomorphometric characteristics, differences between groups significantly increased with age for most variables: at 300 days, atria (+292%), RV (+13%), lungs (+44%), and liver (+23%) weights, LV cavity area (+130%), LV (+364%) and RV (+181%) collagen densities were significantly increased in CMH vs controls, whereas LV (-40%) and RV (-23%) wall thicknesses were significantly decreased. At 260 and 300 days, CMH showed significant pulmonary congestion without hepatic alteration. Bio TO-2 CMH progressively develop an alteration of cardiac function leading to decreased MAP and musculo-cutaneous blood flow associated with cardiac remodeling including atria hypertrophy and LV dilation, wall thinning and a rise in collagen density.

Chronic angiotensin I-converting enzyme inhibition can be associated with aldosterone escape. We investigated the effects of enalapril, spironolactone, and their combination on hemodynamics and cardiac remodeling in cardiomyopathic hamsters to determine whether these drugs could exert additive effects. Cardiomyopathic hamsters, Bio TO-2 dilated strain, were orally treated with enalapril (20 mg. kg. day ) and/or spironolactone (20 mg. kg. day ) according to a 2 x 2 factorial design from 120 days of age. Animals were investigated at 180 (10 animals per group) and 240 (16 animals per group) days of age. Compared with corresponding untreated groups, enalapril significantly decreased mean blood pressure (-18%); enalapril and spironolactone significantly increased cardiac output (+28%, +11%) and femoral blood flow (+10%, +12%) and significantly decreased systemic (-38%, -17%) and femoral (-26%, -13%) vascular resistances. Enalapril and spironolactone significantly decreased left ventricle cavity area (-21%, -26%) and left (-34%, -47%) and right (-37%, -48%) ventricle collagen density. Spironolactone significantly increased left ventricle wall thickness (+4%). There were significant enalapril x spironolactone interactions for most variables (compared with control group, +52%, +36%, +45% for cardiac output; +26%, +28%, +26% for femoral blood flow; -50%, -30%, -45% for systemic vascular resistance; -33%, -20%, -35% for femoral vascular resistance; -27%, -31%, -40% for left ventricle cavity area; and -46%, -58%, -60% for left and -39%, -50%, -66% for right ventricle collagen density in enalapril, spironolactone, and enalapril + spironolactone groups, respectively). In cardiomyopathic hamsters, enalapril and spironolactone in combination did not improve hemodynamics more than enalapril alone but induced stronger effects than each drug alone on cardiac remodeling.

Several methods are used to evaluate gastric emptying (GE) in rats, which is an important endpoint in preclinical drug development. Although phenol red model or monitoring of plasma acetaminophen levels are well-established procedures for GE assessment, their capacity to detect the effects of pharmacological agents has rarely been compared. This study was therefore designed to evaluate clonidine with loperamide and metoclopramide in the two test models. Rats were administered phenol red or acetaminophen test meals. The remaining amount of phenol red in the stomach or the time course of plasma acetaminophen levels was then measured. In the phenol red test, loperamide (8 mg/kg, p.o.) and clonidine (100 μg/kg, s.c.) decreased GE (-88 and -42%, P < 0.001 and P < 0.01, respectively). Metoclopramide (10 mg/kg, s.c.) accelerated GE (+42%, P < 0.01). Loperamide reduced acetaminophen plasma levels (-45% at T15 min, P < 0.05), suggesting a delayed GE. Clonidine and metoclopramide increased acetaminophen plasma levels (+115 and +152% at T15 min, P < 0.05 and P < 0.001, respectively), suggesting an accelerated GE. The three substances did not affect plasma acetaminophen levels when acetaminophen was subcutaneously injected, thereby suggesting that acetaminophen metabolism/excretion was not modified. Whereas the phenol red test allows the evaluation of GE at a single time point, the measurement of plasma acetaminophen levels over the time would appear more informative. Nevertheless, the fact that clonidine, in contrast to expectation, increased plasma acetaminophen levels, suggests that data obtained with the acetaminophen method should be interpreted with caution for new chemical entities susceptible to modify absorption of acetaminophen from the small intestine.