title: In vivo evaluation of left ventricular function in aged SHR by volume loading and the positive inotropic effect of denopamine.
abstract: The positive inotropic effect of denopamine on the hypertrophied heart was studied in 12-months spontaneously hypertensive rats (12-month-SHR) with and without volume loading. Firstly, the influence of volume loading on cardiac function was studied in 12-month-SHR compared with the age-matched normotensive Wistar-Kyoto rats (WKY) and younger WKY (4-month-WKY) as well. Left ventricular end-diastolic pressure (LVEDP) and maximum rate of rise of left ventricular pressure (LV dp/dtmax) were significantly higher in SHR than in WKY and 4-month-WKY. Volume loading (saline, 2 ml/kg/min, i.v., for 10 min) caused a marked increase in LVEDP both in SHR and WKY, but a higher elevation of LVEDP was observed in SHR. LV dp/dtmax, however, was increased in WKY and more markedly in 4-month-WKY, while it was not increased in SHR. Administration of denopamine to SHR at a rate of 1 microgram/kg/min, i.v., for 10 min before and during 10 min of volume loading produced a marked increase in LV dp/dtmax and a significant decrease in LVEDP. Under denopamine infusion, volume loading caused an increase in LV dp/dtmax and produced a LVEDP elevation to a similar level to that of WKY. Denopamine at this dose caused no significant effects on heart rate and mean arterial blood pressure, indicating a selective inotropic action. The present study suggests that functional cardiac reserve is reduced in the aged SHR and that denopamine increases the functional reserve of the hypertrophied heart.
mesh_terms: D000375:Aging; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D001835:Body Weight; D002316:Cardiotonic Agents / Q000494:pharmacology*; D004983:Ethanolamines / Q000494:pharmacology*; D006321:Heart / Q000187:drug effects / Q000502:physiology*; D006339:Heart Rate / Q000187:drug effects; D006352:Heart Ventricles / Q000187:drug effects / Q000254:growth & development; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects*; D009929:Organ Size; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY; D016276:Ventricular Function
chemical_list: D002316:Cardiotonic Agents; D004983:Ethanolamines; C037293:denopamine