| dc.description.abstract | An aqueous extract prepared from the leaves and smaller stems of Leonotis leonurus
was used to investigate the potential effects on certain cardiovascular parameters,
such as left ventricular systolic pressure, end-diastolic pressure, developed pressure,
heart rate, cardiac work and coronary perfusion pressure in isolated rat hearts. Hearts
were perfused at constant flow for 3min using the modified Langendorf! perfused
model of the heart. Effects of adrenaline and digoxin solutions on the isolated heart
were compared to that of the plant extract. Adrenaline produced both positive
inotropic and chronotropic effects. Adrenaline increased (p<O.Ol) the left ventricular
systolic pressure and hence the left ventricular developed pressure by 40.6% and
43.9% at peak, and 24.3% and 31.9%, after 3min, respectively. Simultaneously, the
heart rate and the cardiac work were increased (p<0.01) by 22.5% and 89.4% at peak,
and 24.6% and 63%, after 3rnin, respectively. There were no significant effects on the
left ventricular diastolic pressure and the coronary perfusion pressure. Digoxin
solution (2.5ng/ml) significantly (p<O.Ol) increased the left ventricular systolic
pressure by 5.1% after 3min and the left ventricular diastolic pressure by 9.7% at peak
and 5.3% after 3min. The heart rate was significantly (p<O.OI) decreased by 3.7% at
peak. The cardiac work was increased by 4.5% after 3rnin. Digoxin did not
significantly affect the left end diastolic pressure and the coronary perfusion pressure.
The extract of Leonons leonurus at O.lmg/ml increased (p<O.OI) the left ventricular
systolic pressure and hence the left ventricular diastolic pressure by 9.7% and 10.7%
at peak, and 5.4% and 5.5% after 3rnin, respectively. The cardiac work was increased
(p<O.Ol) by 10.1% at peak. Leonotis leonurus (0.1mg/ml) did not significantly affect
the left ventricular end diastolic pressure, the heart rate and the coronary perfusion
pressure. At 0.5mg/ml, the left ventricular systolic pressure and hence the left
ventricular diastolic pressure were increased (p<0.01) by 14.8% and 15.4% at peak
and 7.4% and 7.8% after 3rnin, respectively with a corresponding decrease (p<O.OI)
in the coronary perfusion pressure of 8.5% at peak and 4.4% after 3rnin. The cardiac
work was increased (p<O.OI) by 13.6% at peak and 5.2% after 3rnin. The extract at
1.0mg/ml increased (p<O.Ol) the left ventricular systolic pressure and hence the left
ventricular diastolic pressure by 25.4% and 29.4% at Peak, and 23.1% and 26.3%
after 3rnin, respectively. The heart rate was reduced (p<O.OI) by 34.7% at peak and
28.3% after 3min. The cardiac work and the coronary perfusion pressure were
decreased (p<O.OI) by 15.9% and 12.1% at Peak and 3.3% and 11.4% after 3rnin.
However, at 2.0mg/ml, the left ventricular systolic pressure and the left ventricular
diastolic pressure were increased (p<O.OI) by 14.9% at peak. The left ventricular
diastolic pressure was decreased (p<O.OI)by 9.8% over the 3rnin. The heart rate was
drastically decreased (p<O.OI) by 42.7% after 3rnin. The cardiac work was reduced
(p<O.Ol) by 48.8% over the 3min period. Also, the coronary perfusion pressure was
decreased (p<0.01) by 16.9% at peak.
Thus, Leonatis leonurus produced both positive inotropic and negative chronotropic
effects after 3min perfusion, accompanied by a decreased coronary perfusion
pressure. Thus, it appears that the extract seemed to contain certain constituents
associated with positive inotropic and negative chronotropic agents as wel! as
constituents associated with coronary vasodilation. However, at the higher
concentration, it seemed to contain some constituents associated with toxic effects on
the isolated heart.
Therefore, further studies are needed to isolate the various constituents and examine
their possible pharmacological effects on the heart individually before it could be
considered safe to recommend this plant for its use in the treatment of cardiovascular
disease. | en_US |
