Intracellular Ca2+ Handling and Vulnerability to Ventricular Fibrillation in Spontaneously Hypertensive Rats

• Published in: Hypertension (Dallas, Tex. 1979) Vol. 30; no. 3; pp. 461 - 467
• Main Authors: Zaugg, Christian E, Wu, Shao T, Lee, Randall J, Wikman-Coffelt, Joan, Parmley, William W
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Philadelphia, PA American Heart Association, Inc 01.09.1997; Hagerstown, MD Lippincott
• Subjects: Animals; Arterial hypertension. Arterial hypotension; Biological and medical sciences; Blood and lymphatic vessels; Calcium - metabolism; Cardiac Pacing, Artificial - methods; Cardiology. Vascular system; Cardiomegaly - complications; Differential Threshold; Disease Susceptibility; Experimental diseases; Hypertension - complications; Hypertension - metabolism; In Vitro Techniques; Intracellular Membranes - metabolism; Male; Medical sciences; Rats; Rats, Inbred SHR - physiology; Rats, Inbred WKY; Stress, Mechanical; Ventricular Fibrillation - etiology; Heart; Hypertension; Arrhythmia; Calcium; Rat; Rodentia; Cardiovascular disease; Hereditary; Excitability disorder; Stress; Ventricular fibrillation; Vertebrata; Mammalia; Heart disease; Animal; Risk factor; Intracellular; Hypertrophy
• ISSN: 0194-911X; 1524-4563
• DOI: 10.1161/01.hyp.30.3.461

Spontaneously hypertensive rats (SHR) with ventricular hypertrophy show an increased vulnerability for the development of potentially lethal ventricular arrhythmias such as ventricular fibrillation (VF). The mechanisms of this increased vulnerability are not fully understood but may be related to abnormal intracellular Ca ([Ca]i) handling under stress conditions. We therefore investigated whether [Ca]i handling is abnormal in hypertrophied hearts of SHR without heart failure during stimulation stress, and if so whether abnormal [Ca]i handling is a determinant of the increased vulnerability to VF in SHR. [Ca]i was measured by indo-1 surface fluorescence in perfused hearts of 8- to 10-month-old control Wistar-Kyoto rats (WKY) and age-matched SHR. The state of [Ca]i handling was analyzed during three different forms of stimulation stressrapid pacing, the long rest period after cessation of rapid pacing, and preprogrammed ventricular stimulation that was simultaneously used for the determination of VF threshold. The pulse number VF threshold was used as an index to determine vulnerability to VF and to analyze the relationship of [Ca]i handling to vulnerability. Although VF thresholds were lower in SHR than in WKY, we found that both demonstrated similar [Ca]i handling during stimulation stress. The extent and rate of [Ca] (i) accumulation during rapid pacing and those of the [Ca]i decline after cessation of pacing were similar in SHR and WKY. In addition, the relationship between [Ca]i and VF threshold was unaltered in SHR. Thus, we conclude that [Ca]i handling is normal in hypertrophied hearts of SHR without heart failure during stimulation stress and that it is not a determinant of the increased vulnerability to VF in SHR. (Hypertension. 1997;30[part 1]:461-467.)