PT  - JOURNAL ARTICLE
AU  - Francis G. Spinale
AU  - Henry H. Holzgrefe
AU  - Rupak Mukherjee
AU  - Maria L. Webb
AU  - R. Barry Hird
AU  - Martyn J. Cavallo
AU  - James R. Powell
AU  - William H. Koster
TI  - Angiotensin-Converting Enzyme Inhibition and Angiotensin II Subtype-1 Receptor Blockade during the Progression of Left Ventricular Dysfunction: Differential Effects on Myocyte Contractile Processes
DP  - 1997 Dec 01
TA  - Journal of Pharmacology and Experimental Therapeutics
PG  - 1082--1094
VI  - 283
IP  - 3
4099  - http://jpet.aspetjournals.org/content/283/3/1082.short
4100  - http://jpet.aspetjournals.org/content/283/3/1082.full
SO  - J Pharmacol Exp Ther1997 Dec 01; 283
AB  - Inhibition of the angiotensin-converting enzyme (ACE) in the setting of chronic left ventricular (LV) dysfunction has been demonstrated to have beneficial effects on survival and symptoms. However, whether ACE inhibition has direct effects on myocyte contractile processes and if these effects are mediated primarily through the AT1angiotensin-II receptor subtype remains unclear. The present project examined the relationship between changes in LV and myocyte function and beta adrenergic receptor transduction in four groups of six dogs each: (1) Rapid Pace: LV failure induced by chronic rapid pacing (4 weeks; 216 ± 2 bpm); (2) Rapid Pace/ACEI: concomitant ACE inhibition (ACEI: fosinopril 30 mg/kg b.i.d.) with chronic pacing; (3) Rapid Pace/AT1 Block: concomitant AT1Ang-II receptor blockade [Irbesartan: SR 47436(BMS-186295) 30 mg/kg b.i.d.] with chronic pacing; and (4) Control: sham controls. With Rapid Pace, the LV end-diastolic volume increased by 62% and the ejection fraction decreased by 53% from control. With Rapid Pace/ACEI, the LV end-diastolic volume was reduced by 24% and the ejection fraction increased by 26% from Rapid Pace only values. Rapid Pace/AT1 Block did not improve LV geometry or function from Rapid Pace values. Myocyte contractile function decreased by 40% with Rapid Pace and increased from this value by 32% with Rapid Pace/ACEI. Rapid Pace/AT1 Block had no effect on myocyte function when compared with Rapid Pace values. With Rapid Pace/ACEI,beta receptor density and cyclic AMP production were normalized and associated with an improvement in myocytebeta adrenergic response compared with Rapid Pace only. Although Rapid Pace/AT1 also normalized betareceptor density, cyclic AMP production was unchanged and myocytebeta adrenergic response was reduced by 15% compared with Rapid Pace only. ACE inhibition with chronic rapid pacing improved LV and myocyte geometry and function, and normalizedbeta receptor density and cyclic AMP production. However, AT1 Ang-II receptor blockade with chronic rapid pacing failed to provide similar protective effects on LV and myocyte geometry and function. These unique findings suggest that the effects of ACE inhibition on LV geometry and myocyte contractile processes in the setting of developing LV failure are not primarily caused by modulation of AT1 Ang-II receptor activation. The American Society for Pharmacology and Experimental Therapeutics