Summary
At 36° C and 2 mM [Ca2+]0, single guinea-pig ventricular myocytes were voltage clamped with patch electrodes. When paired pulsing had potentiated the contraction to the maximum, the cells were shock-frozen for electron probe microanalysis (EPMA). Shock-freezing was timed at the end of diastole (− 80 mV) or at different times during systole (+ 5 mV).
The same paired-pulse protocol was applied to another group of myocytes from which contraction was recorded and [Ca2+]i was estimated by microfluospectroscopy (50 µMNa-Indo-1). In potentiated cells, during the first pulse, contraction peaked within 128±25 ms after start of depolarization. [Ca2+]i peaked within 25 ms to 890 ± 220 nM (mean ± SEM) and fell within 100 ms to about 450 nM.
ΣCa myo,the total calcium concentration in the overlapping myofilaments (A-band), was measured by EPMA in 17 potentiated myocytes. During diastole, ΣCa myo was 2.6±0.4 mmol/kg dry weight (dw), which can be converted to 0.65 mM (mmoles per liter myofibrillar space). Since [Ca2+]i was 180 nM, we estimate that 99.97% of total calcium is bound.
A time-course for systolic ΣCa myo was determined by shock-freezing 13 cells at different times after start of depolarization to +5 mV. ΣCa myo was 5.5 ± 0.3 mmol/kg dw (1.4 mM) after 15–25 ms, 4.6±0.5 mmol/kg dw (1.1 mM) after 30–45 ms, and 3.1 mmol/kg dw (0.8 mM) after 60–120 ms. The fast time-course of ΣCa myo suggests that calcium binds to and unbinds from troponin C at a fast rate. Hence, it is the slow kinetics of the cross-bridges that determines the 130-ms time-to-peak shortening.
Supported by the Deutsche Forschungsgemeinschaft We 879/3-2 and Is 24/7-2
Access this chapter
Tax calculation will be finalised at checkout
Purchases are for personal use only
Preview
Unable to display preview. Download preview PDF.
References
Bendukidze Z, Isenberg G, Klöckner U (1985) Ca-tolerant guinea-pig ventricular myocytes as isolated in the presence of 250 µM free Ca. Basic Res Cardiol 80: 13–18
Blinks JR, Endo M (1986) Modification of myofibrillar responsiveness to CaZ+ as inotropic mechanism. Circulation 73 SIII: 85–98
Fabiato A (1983) Calcium-induced release of calcium from the cardiac sarcoplasmic reticulum. Am J Physiol 245: C1 — C14
Ganitkevich VY, Isenberg G (1991) Depolarization-mediated intracellular Ca’ transients in isolated smooth muscle cells of the guinea pig urinary bladder. J Physiol (in press)
Grynkiewicz G, Poenie M, Tsien RW (1985) A new generation of Ca’ indicators with greatly improved fluorescence properties. J Biol Chem 260: 3440–3450
Shepherd N, Vornanen M, Isenberg G (1990) Force measurements from voltage-clamped guinea-pig ventricular myocytes. Am J Physiol 258: H542–549
Somlyo AV, Gonzales-Serratos H, Shuman H, McClennan G, Somlyo AP (1981) Calcium release and ionic changes in the sarcoplasmic reticulum of tetanized muscle. An electron probe study. J Cell Biol 90: 577–594
Wendt-Gallitelli MF (1986) Ca pools involved in the regulation of cardiac contraction under positive inotropy. X-ray microanalysis of rapid frozen ventricular muscles of the guinea pig. Basic Res Cardiol 81:S1, 25–31
Wendt-Gallitelli MF, Jacob R, Wolburg H (1982) Intracellular membranes as boundaries for ionic distribution. In situ elemental distribution in guina-pig heart muscle in different defined electromechanical coupling states. Z Naturforsch 37c: 712–720
Wendt-Gallitelli MF, Isenberg G (1989) X-ray microanalysis of single myocytes frozen under voltage-clamp conditions. Am J Physiol 256: H574 — H583
Wendt-Gallitelli MF, Isenberg G (1991) Total and free myoplasmic calcium during a contraction cycle: x-ray microanalysis in guinea-pig ventricular myocytes. J Physiol (in press)
Werkheiser WC, Bartley W (1957) The study of steady-state concentrations of internal solutes of mitochondria by rapid centrifugal transfer to a fixation medium. Biochem J 66: 79–91
Author information
Authors and Affiliations
Editor information
Editors and Affiliations
Rights and permissions
Copyright information
© 1991 Springer-Verlag Berlin Heidelberg
About this chapter
Cite this chapter
Wendt-Gallitelli, M.F., Isenberg, G., Voigt, T., Ross, C. (1991). Large and rapid changes of myofibrillar total calcium during the cardiac cycle. Electron probe microanalysis of voltage-clamped guinea-pig ventricular myocytes. In: Gülch, R.W., Kissling, G. (eds) Current Topics in Heart Failure. Steinkopff, Heidelberg. https://doi.org/10.1007/978-3-662-30769-4_9
Download citation
DOI: https://doi.org/10.1007/978-3-662-30769-4_9
Publisher Name: Steinkopff, Heidelberg
Print ISBN: 978-3-7985-0894-1
Online ISBN: 978-3-662-30769-4
eBook Packages: Springer Book Archive