The authors investigated the effect of 24 hours' acute deprivation of food and liquids on lactic dehydrogenase (LDH) activity in the serum, cerebral cortex, subcortical formations and medulla oblongata of 6- and 14-day-old and adult rats. Young rats were starved by separating half of a standard litter from the female for 24 hours. LDH activity was determined by means of Sevac-test-LDH (Imuna, Czechoslovakia) and was expressed in I.U./litre serum or 1 kg tissue wet weight. The samples were prepared at 0 degrees C. LDH activity in the various parts of the CNS was measured in the supernatant of homogenates of the above tissues and the greatest possible destruction of the tissues was ensured by freezing and thawing the homogenates prior to centrifugation. The specimens were incubated at 37 degrees C. Extinction was measured on a SPECOL (G.D.R.) apparatus at 505 nm wavelength. We found that 24 hours' deprivation of food and liquids, together with sensory deprivation in the youngest age groups, significantly reduced LDH activity in both the serum and the cerebral cortex of 6-day-old rats. In adult rats, starvation and thirst raised LDH activity, but the only statistically significant increase was in the medulla oblongata. Under our experimental conditions, LDH activity rose during development by 274% in the cerebral cortex, by 233% in subcortical formations and by 173% in the medulla oblongata. The differences betwen these developmental trends are statistically significant.

Activity of lactate dehydrogenase in serum and cerebral cortex of immature and mature rats after hypobaric hypoxia