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Letter to the editor: Ca2+ mobilization in fetal-human cardiac myocytes is stimulated by isoproterenal and inhibited by ryanodine.

Toraason M; Mathias PI; Richards DE
In Vitro Cell Dev Biol Anim 1998 Jan; 34(1):19-21
Cultured cardiac myocytes from several species are used extensively to assess the cellular physiology, biochemistry, and molecular biology of the heart. Although human cardiac myocytes are investigated, they usually are obtained from diseased myocardium and are limited to right atrial specimens. Therefore, data from human cells in vitro frequently tend to be ancedotal. A few studies have demonstrated that fetal heart tissue obtained from terminated pregnancies can provide a more consistent source of healthy human atrial and ventricle myocytes. One consideration in using such tissue is the immaturity of mechanisms facilitating excitation-contraction. Recently, calcium mobilization during excitation-contraction was characterized in atrial myocytes from 3-d-old and 3-yr-old humans undergoing cardiac surgery. In this study, calcium-induced calcium release from the sarcoplasmic reticulum was the primary regulator of contraction signaling in early postnatal as well as older human atrial atrial myocytes. However, the rate of release of calcium from the sarcoplasmic reticulum increased with age. A similar outcome was reported in a comparison of the responses of neonatal- and adult-rat cardiac myocytes to beta-adrenergic agonists. Maturation was associated with an enhanced repose to beta-adrenergic agonists in terms of contraction, intracellular calcium concentration ([Ca2+]) transient kinetcs, and cAMP levels. Although information on calcium mobilization during excitation and contraction of the postnatal myocardium is limited, information during the fetal period is nonexistent. Therefore, the report represents the first examinaito of {Ca2+], transients in fetal (14-18wk) human myocardium. The results show that at this stage of development [Ca2+], transients during excitation-contraction are qualitatively comparable to neonatal humans and other mammalian species. This was determined by examining the effects of high extracellular calcium, isoproterenol, and ryanodine on [Ca2+], transients in fetal-human ventricular myocytes.
Myocardial-disorders; Myocardium; Cardiac-function; Fetus; Humans; Women
National Institute for Occupational Safety and Health, 4676 Columbia Parkway, Cincinnati, Ohio 45226, USA
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In Vitro Cellular & Developmental Biology. Animal
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