Sodium-dependent short-circuit current across the yolk sac membrane during embryonic development in normal and shell-less cultured chicks.
The transepithelial electrical characteristics of the isolated yolk sac membrane of normal in ovo or shell-less cultured chick embryos were investigated. In normal chicks the potential difference (blood side positive relative to yolk side) and short-circuit current of the membrane increased during development. Ouabain (10(-4) M) on the blood side (basolateral side, serosal side) significantly decreased potential difference and short-circuit current but was without effect on the yolk side (brush border side, mucosal side). Substitution of choline for Na+ in the bathing solutions abolished the potential difference and the short-circuit current; when Na+ replaced choline this effect was reversed. Amiloride added to both sides of the yolk sac membrane had no effect on potential difference or short-circuit current. Injection of aldosterone (50 micrograms) and T3 (10 microM) into yolk did not induce amiloride sensitivity. The short-circuit current was not altered by addition of either glucose or alanine to the bath. The short-circuit current of the yolk sac membrane of shell-less cultured embryos was significantly lower than that of normal controls. Addition of Ca2+ to the serosal bathing medium did not reverse the foregoing condition, but decreased the short-circuit current. It is concluded that the yolk sac short-circuit current is Na+ dependent and increases with developmental age in the chick embryo.
Takada
M
M
Department of Physiology, Saitama Medical School, Japan.
Clark
N B
NB
D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002642:Chick Embryo; D004528:Egg Shell / Q000378:metabolism; D017097:Electric Impedance; D004594:Electrophysiology; D005314:Embryonic and Fetal Development; D005947:Glucose / Q000494:pharmacology; D017136:Ion Transport / Q000187:drug effects; D008564:Membrane Potentials / Q000187:drug effects; D008566:Membranes / Q000187:drug effects / Q000378:metabolism; D010042:Ouabain / Q000494:pharmacology; D012964:Sodium / Q000378:metabolism*; D014284:Triiodothyronine / Q000494:pharmacology; D015017:Yolk Sac / Q000187:drug effects / Q000378:metabolism*
D014284:Triiodothyronine; D010042:Ouabain; D012964:Sodium; D005947:Glucose; D002118:Calcium