Range of messenger action of calcium ion and inositol 1,4,5-trisphosphate.
The range of messenger action of a point source of Ca2+ or inositol 1,4,5-trisphosphate (IP3) was determined from measurements of their diffusion coefficients in a cytosolic extract from Xenopus laevis oocytes. The diffusion coefficient (D) of [3H]IP3 injected into an extract was 283 microns 2/s. D for Ca2+ increased from 13 to 65 microns 2/s when the free calcium concentration was raised from about 90 nM to 1 microM. The slow diffusion of Ca2+ in the physiologic concentration range results from its binding to slowly mobile or immobile buffers. The calculated effective ranges of free Ca2+ before it is buffered, buffered Ca2+, and IP3 determined from their diffusion coefficients and lifetimes were 0.1 micron, 5 microns, and 24 microns, respectively. Thus, for a transient point source of messenger in cells smaller than 20 microns, IP3 is a global messenger, whereas Ca2+ acts in restricted domains.
Allbritton
N L
NL
Department of Cell Biology, Stanford University, CA 94305.
Meyer
T
T
Stryer
L
L
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone / Q000494:pharmacology; D002851:Chromatography, High Pressure Liquid; D003600:Cytosol / Q000378:metabolism; D004058:Diffusion; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism*; D007700:Kinetics; D009865:Oocytes / Q000187:drug effects / Q000378:metabolism*; D015290:Second Messenger Systems; D015398:Signal Transduction; D013729:Terpenes / Q000494:pharmacology; D019284:Thapsigargin; D013997:Time Factors; D014982:Xenopus laevis
D013729:Terpenes; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone; D019284:Thapsigargin; D015544:Inositol 1,4,5-Trisphosphate; D000252:Calcium-Transporting ATPases; D002118:Calcium