Regulación de la utilización del aspartato por los astrocitos durante la prelactancia

During the perinatal period the concentration of N-acetyl-L-aspartate (NAA) produced by neurons increases. This substrate is absorbed by the astrocytes and hydrolyzed via aspartoacylase II (ASPA; EC 3.5.1.15) in acetate and aspartate. We propose that the aspartate may help in fulfilling the astrocyte metabolic requirements during the presuckling period. Objectives. To evaluate the astrocyte ability to use the aspartate as a metabolic substrate in perinatal physiological conditions, and to determine whether the aspartate utilization can be modified by changes in the concentration of glucose (Glc), lactate (LAC) and N-acetyl-L-aspartate (NAA) and whether these variations in concentration can regulate the enzymatic activity of the ASPA. Materials and methods. Quiescent cultures of neonatal astrocytes of Wistar rat were incubated with L-aspartate (0.5 mM) and L-[U-¹⁴C]-aspartate (2 μCi), to assess their ability to use them as oxidative and lipogenic substrates. The effect of varying concentrations of Lac, Glc and NAA on the use of aspartate (radiometry method) and the ASPA activity (spectrophotometry method) was evaluated in both presuckling and adult physiological conditions. Results. Astrocytes are able to use aspartate 87 times more as an oxidative substrate than a lipogenic substrate. Conclusions. The use of aspartate and its destiny are affected significantly (p<0.05) by the concentrations of Lac, Glc and NAA. ASPA has a high activity being regulated by lactate availability and the increased availability of glucose.