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Sodium-dependent short-circuit current across the yolk sac membrane during embryonic development in normal and
Insights
The chick embryo yolk sac membrane
Area of Science:
- Developmental biology
- Physiology
- Epithelial transport
Background:
- The yolk sac membrane plays a crucial role in nutrient and ion transport during embryonic development.
- Understanding its electrical characteristics is key to comprehending chick embryo physiology.
Purpose of the Study:
- To investigate the transepithelial electrical properties of the chick embryo yolk sac membrane.
- To determine the developmental changes and ionic dependencies of yolk sac membrane function.
Main Methods:
- Isolated yolk sac membranes from in ovo and shell-less cultured chick embryos were used.
- Transepithelial electrical potential difference and short-circuit current were measured.
- The effects of ouabain, Na+ substitution, amiloride, aldosterone, T3, glucose, alanine, and Ca2+ were assessed.
Main Results:
- Potential difference and short-circuit current increased with developmental age in normal chick embryos.
- Ouabain significantly reduced electrical characteristics when applied to the blood side.
- Sodium (Na+) dependence was confirmed, while amiloride had no effect.
- Shell-less cultured embryos exhibited lower short-circuit current compared to controls.
Conclusions:
- The yolk sac membrane's short-circuit current is primarily dependent on sodium (Na+) transport.
- Electrical activity increases with embryonic development.
- Environmental factors, such as shell-less culture, can impact yolk sac membrane function.
Abstract:
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.