Effects of ageing and increased haemolysis on the levels of dolichol in rat spleen

Dolichol is a long-chain polyisoprenoid. No enzyme pathway for dolichol degradation was discovered. Dolichol accumulates in human and rodent tissues during ageing. Red blood cells contain a larger amount of dolichol and red blood cell life span is shorter in older rats. The effects of age and of the load of dolichol from red blood cell degradation on the ageing-associated accumulation of dolichol in spleen were studied in 2, 6, 12, 18 and 24 month-old male Sprague Dawley rats fed ad libitum (AL) or on an anti-ageing dietary regimen (EOD). Tissue dolichol was extracted and assayed by HPLC [J. Gerontol. 53A (1998) B87]. Levels of dolichol increased in spleen, liver, kidney and muscle in parallel fashion from the age of 2 to 12 months. Unexpectedly, spleen dolichol decreased in older rats whereas liver, kidney and muscle dolichol increased significantly. The effects of haemolysis on spleen dolichol were tested by the administration of phenylhydrazine. Results show that haemolysis does not increase, but rather decreases the levels of dolichol in erythroclastic organs. It is concluded that the levels of spleen dolichol may decrease in the absence of any known enzymatic degradative pathway if the spleen and its resident phagocytes are forced to cope with a higher number of red blood cells to be cleared. Free-radical mediated decomposition of dolichol by phagocytic cells during erythrophagocytosis might be involved in the process. (C) 2001 Elsevier Science Inc. All rights reserved.