Effect of hypertonicity on contractility of isolated working rat left ventricle.
OBJECTIVE
The aim was to evaluate the effect of hypertonic perfusate on isolated left ventricular mechanical and energetic characteristics.


METHODS
An isolated working rat heart model was perfused with a hyponatraemic Krebs-Heinseleit bicarbonate buffer (240 mOsmol.litre-1). To this buffer was added increasing amounts of mannitol to achieve 280, 320, and 360 mOsmol.litre-1 perfusates.


RESULTS
Left ventricular peak pressure, maximum time derivative of left ventricular pressure (dP/dtmax), and end systolic pressure were all increased to a maximum value at 280 or 320 mOsmol.litre-1 perfusate tonicity. A similar response was evident with cardiac output, which changed from 33.7(SEM 0.6) to 43.5(0.8) ml.min-1 following changing the perfusate tonicity from 240 to 280 mOsmol.litre-1 (p less than or equal to 0.003). However, increasing perfusate tonicity further decreased cardiac output to 36.5(1.3) ml.min-1 at 360 mOsmol.litre-1. Maximal left ventricular elastance remained unchanged during perfusion with increasing perfusate tonicities.


CONCLUSIONS
Changing perfusate osmolality using mannitol has a positive inotropic effect at low osmolalities and a negative inotropic effect at perfusate osmolality greater than 320 mOsm.litre-1.
Ben-Haim
S A
SA
Rappaport Family Institute for Research in the Medical Sciences, Technion-Israel Institute of Technology, Haifa.
Hayam
G
G
Edoute
Y
Y
Better
O S
OS
D000818:Animals; D006982:Hypertonic Solutions / Q000494:pharmacology*; D008297:Male; D008353:Mannitol / Q000494:pharmacology; D009200:Myocardial Contraction / Q000187:drug effects*; D009924:Organ Culture Techniques; D009994:Osmolar Concentration; D010477:Perfusion; D051381:Rats; D011919:Rats, Inbred Strains; D016277:Ventricular Function, Left / Q000187:drug effects*
D006982:Hypertonic Solutions; D008353:Mannitol