Effects of changes in hydromineral balance on rat brain aspartyl, arginyl, and alanyl aminopeptidase activities

In order to examine the possible relationship between the processing and inactivation roles of aminopeptidases and the disruption of water-electrolyte balance, we measured the activities of aspartyl aminopeptidase (Asp-Ap), arginyl aminopeptidase (Arg-Ap) and alanyl aminopeptidase (Ala-Ap) in certain brain areas (hypothalamus, hippocampus, thalamus and brain cortices) and in the pituitary gland in several models of hydrosaline change. The activity of hypothalamic membrane-bound Asp-Ap significantly decreased (more than 50%) following treatments which induced a hypovolemic state. Aminopeptidase M activity (membrane-bound Ala-Ap activity with low sensitivity to puromycin) was also significantly decreased by 53 % in the thalamus of rats under conditions of hypovolemia plus hyperosmolality in comparison to the control group. These results indicate that aminopeptidases in the central nervous system may be involved in the physiological regulation of hydromineral balance.