Effects Of Magnesium Lithospermate B On Myocardial Microperfusion In SD Rats

Magnesium Lithospermate B (MLB) is a major aqueous extract ingredient of Chinese herb Radix Salvia miltiorrhiza (danshen) and the pharmacological profile of MLB has been extensively characterized. Laser Doppler flowmetry is widely used in determining microperfusion, but rarely in the field of coronary microcirculation. In this in vivo study we assessed myocardial microperfusion by means of laser Doppler flowmetry in the beating heart of SD rats, with ascending arotic flow and other hemodynamic parameters recorded simultaneously. We aimed to establish a method for myocardial microperfusion assessment using laser Doppler technique quantitatively and to estimate the effects of MLB on myocardial micorperfusion in SD rats.A needle probe with a hold was placed appropriately adherent to the epicardium of the left ventricular myocardium close to the left anterior descending coronary artery in an anaesthetized open-chest rat. The responses of myocardial microperfusion to two vasodilators (captopril and nifedipine) and a vasoconstrictor (pituitrin) were tested. The waveform of myocardial microperfusion that behaved in a phasic fashion is predominately diastolic and its phase is opposite to the ascending aortic flow. Intravenous administration of 5 mg/kg and 10 mg/kg captopril exhibited an increasing effect on myocardial microperfusion by 10±2% (P<0.01), 7±2% (P<0.01), respectively. In the initial period a sustained elevation with the peak of 7±1% (P<0.01) in the myocardial microperfusion was observed after nifedipine 75μg/kg intravenous administration. Meanwhile, an increase of cardiac index was also observed after bolus injection of both drugs. Furthermore, pituitrin (0.5 IU/kg, iv.) resulted in a significant decrease in myocardial microperfusion by 28±10% (P<0.05) maximally. Thus, laser Doppler flowmetry provides a means of assessing myocardial microperfusion in beating rat heart, and can be applied to evaluate the responses of coronary microcirculation to drugs.We found that MLB ameliorated coronary microcirculation. MLB 30 and 60 mg/kg iv. increased the myocardial microperfusion by 6±1% and 10±2% (P<0.01), respectively. Both doses of MLB exerted an increasing effect on cardiac index dose-dependently; however, they resulted in opposite responses in mean arterial pressure (MAP). MLB 30 mg/kg produced hyoptension about 15 min after intravenous administration while 60 mg/kg MLB caused an increase in MAP and did not revert to the baseline until 10 min later.In conclusion, these results suggest that laser Doppler flowmetry provides a means of assessing myocardial microperfusion in rats, and MLB ameliorated coronary microcirculation.