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Left ventricular length dependent activation in the isovolumetric rat heart
I Stefanon1, D V Vassallo, J G Mill
1Departamento de Ciências Fisiológicas, Universidade Federal do Espirito Santo, Vitória, Brasil.
Study Objective:
The aim of the study was to examine, in a whole heart preparation, the relationship between length changes in cardiac muscle and tension development and length dependent activation.
Design:
Rat hearts were perfused by the Langendorff technique and isovolumetric pressure changes in the left ventricle, produced by increasing diastolic pressures (0, 5, 10, 15, 20, 25 mm Hg), were studied at different calcium concentrations (0.5, 1.25, 2.5, 3.75 mmol.litre-1).
Experimental Materials:
20 whole heart preparations were obtained from albino rats of either sex, weight 180-240 g (females) and 220-330 g (males).
Measurements And Main Results:
In a comparison of ventricular diastolic upsilon systolic pressure curves, normalised with respect to maximum isovolumetric systolic pressure, there was a separation and an upward displacement of the curves with increments in calcium concentration in the perfusate.
Conclusions:
The results show, as in isolated preparations, that there is length dependent activation in the whole rat heart.
