MALNUTRITION INCREASES NEUROFILAMENT SUBUNITS CONCENTRATION IN RAT CEREBELLUM

We reported previously that the expression of neurofilaments in rat ce rebral cortex is sensitive to early malnutrition. Different cerebral s tructures respond differently to the same stimulus, therefore we under took the present study to determine whether early malnutrition affects the expression and in vitro incorporation Of P-32 in neurofilament su bunits from rat cerebellum. Wistar rats were fed a normal protein (25% casein) or an isoenergetic low protein (8% casein) diet from the day of parturition to the day pups were weaned. Some litters were sacrific ed at weaning; others (both normal and malnourished animals) received a 25% protein diet until day 90, when they were sacrificed. Intermedia te filament preparations were obtained by extraction of the tissue wit h a high salt phosphate-buffered solution containing 1% Triton X-100. The pellet containing the bulk of neurofilament proteins identified as 200, 150, and 68 kDa subunits was scanned following one-dimensional g el electrophoresis. In vitro P-32 incorporation was measured in cytosk eletal proteins obtained by the method of axonal flotation. Total prot ein concentration in the cerebellum was not altered with malnutrition. Conversely, the concentration of the 200 and 150 kDa subunits increas ed in young rats, but this effect was absent in adults. However, in vi tro P-32 incorporation into cytoskeletal proteins was not altered in m alnourished animals. Early malnutrition seems to interfere with mechan isms that regulate neurofilament formation during the period of maxima l cerebellum development. However, this effect was absent after the re sumption of a normal diet, suggesting transient alterations probably n ot related to in vitro P-32 incorporation.