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Enhanced spontaneous calcium efflux and decrease of calcium-dependent calcium release from the isolated perfused heart of spontaneously hypertensive rats.

Y Hojo·H Ebata·U Ikeda·Y Tsuruya·T Natsume·K Shimada
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Abstract

OBJECTIVE: The aim of this study was to clarify the further details of calcium handling in hypertension. DESIGN: By preserving the physiological environment of cell membrane, whole hearts were used for comparison of calcium flux between spontaneously hypertensive rats (SHR) and Wistar-Kyoto (WKY) rats. METHODS: Hearts from SHR and WKY rats were perfused with Krebs-Henseleit solution under constant flow and the effluent collected. RESULTS: After labelling of the heart with 45Ca2+ (100 mumol/l), 45Ca2+ binding was found to be saturated, and washing with calcium-free perfusion solution showed two exponential curves for calcium dissociation, indicating a fast (alpha-) and slow (beta-) phase. The half-lives of the beta-phase for both 4- and 8-week-old SHR were significantly shorter than those for age-matched WKY. Also in this phase, infusion of non-radioactive Ca2+ caused a transient dose-dependent release of 45Ca2+. A significant reduction in the amount of 45Ca2+ release induced by 2 mmol/l Ca2+ was observed in both 4- and 8-week-old SHR compared with age-matched WKY rats. Infusion of lanthanum, caffeine, ionomycin (calcium ionophore) and treatment of the hearts with ethyleneglycol-bis-(beta-aminoethylether)-N,N,N,',N'-tetraac etic acid did not alter 45Ca2+ release by non-radioactive Ca2+. From these observations, 45Ca2+ is presumably released from the intracellular calcium pool, and not from extracellular binding sites or sarcoplasmic reticulum. CONCLUSIONS: These findings suggest that an abnormal calcium-handling defect (enhanced calcium efflux and reduction of membrane-bound Ca2+) exists under physiological conditions before and after the onset of hypertension, and that this may be a primary characteristic of SHR.

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AgingAnimalsCaffeineCalciumCalcium RadioisotopesEgtazic AcidHalf-LifeHeartHypertensionIn Vitro TechniquesIonomycinLanthanumMaleMyocardiumRatsRats, Inbred SHRRats, Inbred WKYComparative StudyJournal ArticleResearch Support, Non-U.S. Gov't

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Y Hojo, H Ebata, U Ikeda, Y Tsuruya, T Natsume, K Shimada. 1992. Enhanced spontaneous calcium efflux and decrease of calcium-dependent calcium release from the isolated perfused heart of spontaneously hypertensive rats.. https://doi.org/10.1097/00004872-199206000-00003

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