Gap junction channel. Its aqueous nature as indicated by deuterium oxide effects
The effects of temperature and solvent substitution with deuterium oxide (D2O) on axoplasmic (ga) and gap junctional (gj) conductances were examined in the earthworm septate median giant axon (MGA). The temperature coefficients (Q10) for ga and gj were 1.4 and 1.5, respectively, between 5 and 15 degrees C. Substitution with D/sub 2/O rapidly reduced both ga and gj by 20% and increased the Q10's to 1.5 and 1.8, respectively. The reduction in ga upon substitution with D/sub 2/O and with cooling in either solvent reflects the changes that occur in solvent viscosity, which indicates that ion mobility in axoplasm, as in free solution, is primarily governed by viscous properties of the solvent. The similar initial reduction observed for gj suggests that solvent occupies the gap junction channel volume and influences transjunctional ion mobility. With time there was a further reduction in gj at 20 degrees C and a larger Q10 in D/sub 2/O. The enhanced effects of D/sub 2/O on gj cannot be accounted for by solvent viscosity alone and may be due to an increased hydration of the channels and/or the transport ions and by isotope effects of hydrogen-deuterium exchange on the channel protein that reduce gj.
- Research Organization:
- Health Science Center at Stony Brook, NY
- OSTI ID:
- 6756768
- Journal Information:
- Biophys. J.; (United States), Vol. 5
- Country of Publication:
- United States
- Language:
- English
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551001* - Physiological Systems- Tracer Techniques