Apical Membrane Vesicles of ADH-stimulated Toad Bladder are Highly Water Permeable
|Title:||Apical Membrane Vesicles of ADH-stimulated Toad Bladder are Highly Water Permeable|
|Authors:||Harris, H. William; Handler, Joseph S.; Blumenthal, Robert|
|Publisher:||American Journal of Physiology|
|Date Published:||February 01, 1990|
This translation by the NDI Foundation is to assist the lay reader. To provide a clear, accessible interpretation of the original article, we eliminated or simplified some technical detail and complicated scientific language. We concentrated our translation on those aspects of the article dealing directly with NDI. The NDI Foundation thanks the researchers for their work toward understanding and more effectively treating this disorder.
© Copyright NDI Foundation 2007 (JC)
According to the shuttle hypothesis, when ADH is present in the granular cell, it induces the aggrephores to travel from the interior of the cell to the apical membrane and fuse with it. Once fused, the water channels that are inside it are inserted into the apical membrane. The apical membrane now is filled with water channels so water can now flow through it much more easily and in greater volume than before. Another way of saying this is that the water channels dramatically increase the apical membrane's Pf.
When ADH absents itself from the granular cell, the water channels are retrieved from the apical membranes, and the apical membrane Pf returns to its normal low state. The water channels are taken back into the cell in the aggrephores and in aggregate rich sections of the apical membrane.
Harris, et al., wanted to measure the Pf of these aggrephores after they returned from the apical membrane to the interior of the cell. They did this by loading the aggrephores with self-quenching flurophore carboxyfluorescein (CF). Quenching is any type of interference which reduces the intensity of fluorescence. By adding the CF to the aggrephores and adding an anti-CF antibody to quench all the CF outside the aggrephores, the authors were able to track the CF in the aggrephores.
They discovered that the retrieved aggrephores had an extremely high Pf, comparable to the Pf of red blood cells (minus their hemoglobin) that they measured under identical circumstances. This high Pf strongly supports the idea that they are filled with particle aggregates (i.e., water channels), thus supporting the shuttle hypothesis described above.