Mitochondrial Ca2+ homeostasis during Ca2+ influx and Ca2+ release in gastric myocytes from Bufo marinus
Department of Physiology
Animals; Bufo marinus; Caffeine; Calcium; Cells, Cultured; Cytoplasm; Electric Stimulation; Fluorescent Dyes; Heterocyclic Compounds, 3-Ring; Homeostasis; Intracellular Membranes; Membrane Potentials; Microscopy, Video; Mitochondria; Muscle, Smooth; Patch-Clamp Techniques; Sarcoplasmic Reticulum; Stomach
Life Sciences | Medicine and Health Sciences
1. The Ca(2+)-sensitive fluorescent indicator rhod-2 was used to monitor mitochondrial Ca2+ concentration ([Ca2+]m) in gastric smooth muscle cells from Bufo marinus. In some studies, fura-2 was used in combination with rhod-2, allowing simultaneous measurement of cytoplasmic Ca2+ concentration ([Ca2+]i) and [Ca2+]m, respectively. 2. During a short train of depolarizations, which causes Ca2+ influx from the extracellular medium, there was an increase in both [Ca2+]i and [Ca2+]m. The half-time (t1/2) to peak for the increase in [Ca2+]m was considerably longer than the t1/2 to peak for the increase in [Ca2+]i. [Ca2+]m remained elevated for tens of seconds after [Ca2+]i had returned to its resting value. 3. Stimulation with caffeine, which causes release of Ca2+ from the sarcoplasmic reticulum (SR), also produced increases in both [Ca2+]i and [Ca2+]m. The values of t1/2 to peak for the increase in [Ca2+] in both cytoplasm and mitochondria were similar; however, [Ca2+]i returned to baseline values much faster than [Ca2+]m. 4. Using a wide-field digital imaging microscope, changes in [Ca2+]m were monitored within individual mitochondria in situ, during stimulation of Ca2+ influx or Ca2+ release from the SR. 5. Mitochondrial Ca2+ uptake during depolarizing stimulation caused depolarization of the mitochondrial membrane potential. The mitochondrial membrane potential recovered considerably faster than the recovery of [Ca2+]m. 6. This study shows that Ca2+ influx from the extracellular medium and Ca2+ release from the SR are capable of increasing [Ca2+]m in smooth muscle cells. The efflux of Ca2+ from the mitochondria is a slow process and appears to be dependent upon the amount of Ca2+ in the SR.
J Physiol. 2000 Feb 1;522 Pt 3:375-90.
The Journal of physiology
Drummond, Robert M.; Mix, Christian H.; Tuft, Richard A.; Walsh, John V.; and Fay, Fredric S., "Mitochondrial Ca2+ homeostasis during Ca2+ influx and Ca2+ release in gastric myocytes from Bufo marinus" (2000). Open Access Articles. 1492.