Rapid amino acid uptake in rat pituitary neural lobe during functional stimulation by chronic dehydration.

We studied the transfer of a small neutral amino acid, alpha-aminoisobutyric acid, from arterial blood into the pituitary neural lobe in normal rats and in rats deprived of water for 5 days. A threefold increase in the neural lobe uptake of the amino acid was found in the chronically dehydrated rats. Possible causes for this effect include enlargement of the capillary and pituicyte membrane surface areas available for solute flux and increased permeability of these membranes. Such functional and structural alterations may be associated with an increase in protein turnover in the neural lobe during dehydration.