Regional variations in the tightness of the ectodermal epithelium in the developing chick embryo: a study using ion-sensitive microelectrodes.
In 2-day-old avian embryos there is a rosto-caudal gradient of interstitial pH (Gillespie and McHanwell: Cell Tissue Res., 247:445-451, '87). Neither the developmental significance nor the basic cellular mechanisms underlying this phenomenon has been studied. The present paper provides information about the interstitial potassium and calcium ion concentrations and the movement of these ions across the ectodermal epithelium. The data suggests a possible explanation for the longitudinal pH gradient in the embryo. The concentrations of potassium and calcium ions in the interstitial spaces were measured with ion-sensitive and conventional microelectrodes. In embryos bathed in solution containing 1 mM potassium, the potassium concentration in the region of the mesencephalon was 5.1 +/- 0.7 mM while in the region of the unsegmented mesoderm it was significantly lower at 3.3 +/- 0.4 mM (mean +/- S.E., n = 16). If embryos are exposed to extra-embryonic solutions containing 30 mM potassium, the K+ concentration in the mesencephalon is 13.0 +/- 0.8 mM and higher at 15.4 +/- 1.2 mM in the unsegmented mesoderm (n = 12). In embryos bathed in solutions containing 0.1 mM calcium, the interstitial calcium was found to be 1.1 +/- 0.52 mM in the mesencephalon and 0.42 +/- 0.19 mM in the unsegmented mesoderm (n = 3). In comparison, embryos bathed in solution containing 10 mM calcium had 1.9 +/- 0.2 mM rostrally compared to 3.71 +/- 0.63 mM caudally (n = 10). Thus it is possible to generate intra-embryonic ion gradients dependent upon the extra-embryonic ion concentration.(ABSTRACT TRUNCATED AT 250 WORDS)
Carnan
E
E
Department of Physiological Sciences, Medical School, University of Newcastle, England.
Gillespie
J I
JI
D000375:Aging / Q000378:metabolism; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002118:Calcium / Q000378:metabolism*; D002642:Chick Embryo; D004475:Ectoderm / Q000378:metabolism*; D004848:Epithelium / Q000378:metabolism; D005110:Extracellular Space / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D008839:Microelectrodes; D011188:Potassium / Q000378:metabolism*; D011190:Potassium Cyanide / Q000494:pharmacology
D011190:Potassium Cyanide; D011188:Potassium; D002118:Calcium