AJP - Heart and Circulatory Physiology, Vol 258, Issue 1 183-H190, Copyright © 1990 by American Physiological Society
Atriopeptin 24 regulates myocardial function via Frank-Starling mechanism in conscious dogs
M. B. Patel and T. H. Hintze
Department of Physiology, New York Medical College, Valhalla 10595.
Recent studies have shown that the infusion of atriopeptins decreases blood
volume because of the diuresis and also because of changes in vascular
volume. In dogs chronically instrumented for the measurement of left
ventricular pressure and internal left ventricular diameter, infusion of
atriopeptin 24 (500 ng.kg-1.min-1 for 1 h), steady-state plasma levels of
6,000 pg/ml resulted in 5.9 +/- 1.7% decrease in left ventricular (LV)
end-diastolic diameter (EDD) from 34.7 +/- 2.3 mm (P less than 0.05) and no
significant change in LV first derivative of pressure with time (dP/dt), LV
first derivative of dimension with time, LV dP/dt divided by internal
diastolic circumference or percent shortening. Hematocrit increased from 42
to 46% (P less than 0.05). During pacing, infusion of atriopeptin 24 still
reduced LV EDD by 7.5 +/- 1.8% from 32 +/- 2.8 mm (P less than 0.05),
although there were no changes in the indexes of inotropic state. These
results were unaffected by combined autonomic receptor blockade or by
ganglionic blockade. Inflation of a hydraulic occluder around the aorta
during the infusion of atriopeptin 24 to return LV EDD to preinfusion
levels did not cause any index of myocardial contractility to increase
significantly. At lower infusion rates that resulted in plasma atriopeptin
levels of 2,000 pg/ml, atriopeptin 24 still reduced LV EDD without effect
on inotropic state. Thus in the conscious dog, atriopeptins reduce preload
independent of neuronal influences and without affecting inotropic state.
