Spatial and temporal patterns of intracellular calcium in colonic smooth muscle.
Intracellular calcium [Ca2+]i measurements in cell suspension of gastrointestinal myocytes have suggested a single [Ca2+]i transient followed by a steady-state increase as the characteristic [Ca2+]i response of these cells. In the present study, we used digital video imaging techniques in freshly dispersed myocytes from the rabbit colon, to characterize the spatiotemporal pattern of the [Ca2+]i signal in single cells. The distribution of [Ca2+]i in resting and stimulated cells was nonhomogeneous, with gradients of high [Ca2+]i present in the subplasmalemmal space and in one cell pole. [Ca2+]i gradients within these regions were not constant but showed temporal changes in the form of [Ca2+]i oscillations and spatial changes in the form of [Ca2+]i waves. [Ca2+]i oscillations in unstimulated cells (n = 60) were independent of extracellular [Ca2+] and had a mean frequency of 12.6 +/- 1.1 oscillations per min. The baseline [Ca2+]i was 171 +/- 13 nM and the mean oscillation amplitude was 194 +/- 12 nM. Generation of [Ca2+]i waves was also independent of influx of extracellular Ca2+. [Ca2+]i waves originated in one cell pole and were visualized as propagation mostly along the subplasmalemmal space or occasionally throughout the cytoplasm. The mean velocity was 23 +/- 3 microns per sec (n = 6). Increases of [Ca2+]i induced by different agonists were encoded into changes of baseline [Ca2+]i and the amplitude of oscillations, but not into their frequency. The observed spatiotemporal pattern of [Ca2+]i regulation may be the underlying mechanism for slow wave generation and propagation in this tissue. These findings are consistent with a [Ca2+]i regulation whereby cell regulators modulate the spatiotemporal pattern of intracellularly generated [Ca2+]i oscillations.
Department of Medicine, VA Wadsworth Medical Center, Los Angeles, California.
E A
EA
Mayer
A
A
Kodner
X P
XP
Sun
J
J
Wilkes
D
D
Scott
G
G
Sachs
D000818:Animals; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002217:Carbachol / Q000494:pharmacology; D003106:Colon / Q000378:metabolism*; D007091:Image Processing, Computer-Assisted; D066298:In Vitro Techniques; D009130:Muscle, Smooth / Q000166:cytology / Q000378:metabolism* / Q000648:ultrastructure; D011188:Potassium / Q000378:metabolism; D011817:Rabbits; D012519:Sarcoplasmic Reticulum / Q000378:metabolism; D015398:Signal Transduction; D013373:Substance P / Q000031:analogs & derivatives / Q000494:pharmacology
C062618:substance P, Sar(9)-Met(O2)(11)-; D013373:Substance P; D002110:Caffeine; D002217:Carbachol; D011188:Potassium; D002118:Calcium