AJP - Cell Physiology, Vol 260, Issue 5 C1028-C1038, Copyright © 1991 by American Physiological Society
Humoral factors reduce gap junction sensitivity to cytoplasmic pH. I. Organ ablation studies
A. P. Moreno, D. C. Spray and F. Ramon
Departmento de Fisiologia, Biofisica y Neurociencias, Centro de Investigacion y de Estudios Avanzados, Mexico DF.
The sensitivity of gap junctions connecting crayfish lateral axons to
uncoupling by axoplasmic acidification was studied after altering the
hormonal balance of animals by 1) ablation of eyestalks or sinus glands or
2) inducing long-lasting defensive posturing behavior (stress). Internal pH
(pHi) was measured with microelectrodes, and junctional resistance (Rj) was
calculated from input and transfer resistances. In isolated nerve cords
from intact animals, the maximal Rj (Rjmax) reached after acidification
varied diurnally (Rjmax approximately 10 and 0.6 M omega at 0900 and 1800
h, respectively). Basal Rj (20-30 k omega) did not change during the 24-h
period. Organ ablation (eyestalks or sinus glands) or stress rendered gap
junctions less sensitive to uncoupling by low pHi within 1 h or 2 days;
recovery toward control values had different time courses. The reduced pH
sensitivity of crayfish junctions seen after eyestalk ablation is
attributable to stress in its early phase (lasting 1-2 days) and to
ablation of the endocrine organs in its late phase (2-7 days). No striking
structural differences accompanied these changes, indicating that the
altered properties are not due to major changes in gap junction expression.
