BACKGROUND AND PURPOSEPreviously, a systems pharmacology model was developed characterizing drug effects on the interrelationship between mean arterial pressure (MAP), cardiac output (CO) and total peripheral resistance (TPR). The present investigation aims to (i) extend the previously developed model by parsing CO into heart rate (HR) and stroke volume (SV) and (ii) evaluate if the mechanism of action (MoA) of new compounds can be elucidated using only HR and MAP measurements.
EXPERIMENTAL APPROACHCardiovascular effects of eight drugs with diverse MoAs (amiloride, amlodipine, atropine, enalapril, fasudil, hydrochlorothiazide, prazosin and propranolol) were characterized in spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto (WKY) rats following single administrations of a range of doses. Rats were instrumented with ascending aortic flow probes and aortic catheters/radiotransmitters for continuous recording of MAP, HR and CO throughout the experiments. Data were analysed in conjunction with independent information on the time course of the drug concentration following a mechanism-based pharmacokinetic-pharmacodynamic modelling approach.
KEY RESULTSThe extended model, which quantified changes in TPR, HR and SV with negative feedback through MAP, adequately described the cardiovascular effects of the drugs while accounting for circadian variations and handling effects.
CONCLUSIONS AND IMPLICATIONSA systems pharmacology model characterizing the interrelationship between MAP, CO, HR, SV and TPR was obtained in hypertensive and normotensive rats. This extended model can quantify dynamic changes in the CVS and elucidate the MoA for novel compounds, with one site of action, using only HR and MAP measurements. Whether the model can be applied for compounds with a more complex MoA remains to be established. Abbreviations amp, amplitude; BSL_CO, baseline value of cardiac output; BSL_HR, baseline value of heart rate; BSL_MAP, baseline value of mean arterial pressure; BSL_SV, baseline value of stroke volume; BSL_TPR, baseline value of total peripheral resistance; C, drug concentration in plasma; CO, cardiac output; Emax, maximum effect; FB, negative feedback of mean arterial pressure; FB0, feedback of a typical subject; FB0_MAP, exponent of the power relationship between FB and the individual BSL_MAP; HCTZ, hydrochlorothiazide; hor, horizontal displacement; HR, heart rate; Kin_HR, zero-order production rate constant of HR; Kin_SV, zero-order production rate constant of stroke volume; Kin_TPR, zero-order production rate constant of total peripheral resistance; kout_HR, first-order dissipation rate constant of HR; kout_SV, first-order dissipation rate constant of stroke volume; kout_TPR, first-order dissipation rate constant of total peripheral resistance; LVFT, left ventricular filling time; MAP, mean arterial pressure; MoA, mechanisms of action; MVOF, minimum value of the objective function;