Ca2+ wave dispersion and spiral wave entrainment in Xenopus laevis oocytes overexpressing Ca2+ ATPases.
Complex, spatiotemporal patterns of intracellular Ca2+ release in Xenopus oocytes can be accounted for by the operation of two fundamental processes: Ca2+ release from the endoplasmic reticulum (ER) via the inositol 1,4,5-trisphosphate receptor (IP3R) with its inherent dependency on cytosolic Ca2+, and Ca2+ uptake via Ca2+ ATPases. Overexpression of sarco-endoplasmic reticulum Ca2+ ATPases (SERCAs) in Xenopus oocytes, increases IP3-induced Ca2+ wave frequency and amplitude [1-3]. This effect can be attributed to an increased removal of cytoplasmic Ca2+ and more efficient refilling of Ca2+ stores. By overexpressing SERCA isoforms, we report here that Ca2+ waves exhibit dispersion [4-6]. At wavelengths greater than 60 microns, wave velocity is constant. However, wave velocity and amplitude progressively decreases at smaller wavelengths. Below gamma approximately 20 microns, Ca2+ waves disperse and fail to propagate. In oocytes exhibiting both spiral and target patterns of Ca2+ release, spiral waves had higher frequencies and showed entrainment of the surrounding regions. These properties are characteristic of a classical excitable medium [4-6].
Lechleiter
J D
JD
Department of Molecular Medicine/Institute of Biotechnology, University of Texas HSC, San Antonio 78245, USA. lechleiter@uthscsa.edu
John
L M
LM
Camacho
P
P
D000818:Animals; D002118:Calcium / Q000378:metabolism / Q000502:physiology*; D000252:Calcium-Transporting ATPases / Q000096:biosynthesis*; D004721:Endoplasmic Reticulum / Q000201:enzymology; D009865:Oocytes / Q000201:enzymology / Q000502:physiology*; D012519:Sarcoplasmic Reticulum / Q000201:enzymology; D014982:Xenopus laevis
D000252:Calcium-Transporting ATPases; D002118:Calcium