Pineal Gland Morphology in Rats With Experimentally Induced Protein‐Calorie Malnutrition

The morphology of the pineal gland was studied in protein‐calorie‐malnourished (PCM) rats. Twenty‐day‐old male Sprague‐Dawley rats were placed in a 14:10 photoperiod and fed either an 8% low protein diet (LPD) or a standard laboratory diet (SLD) containing 27% protein for 30 d. At 50 d of age, rats from both animal groups were sacrificed at 0900 h and at 2400 h, and the pineal glands were immersion‐fixed for either light or electron microscopic analysis. The cytoplasm and nuclei of the pinealocytes from the SLD‐fed rats were consistently larger than those of the animals maintained on the LPD. Additionally, the lipid droplets were larger and more prominent in the controls at both 0900 h and 2400 h. Even though the size of these inclusions did not vary among animals given the same diet as a function of the time of sacrifice, they were more numerous in both the well‐fed and malnourished rats during the dark phase of the photoperiod. In contrast neither diet nor sampling time affected the size or number of pinealocyte mitochondria. These morphological observations lend further support to the premise than PCM impairs the cellular activity of the pinealocytes.