On the effects of nutrition on the metabolism of foreign compounds in the liver of reindeer (Rangifer tarandus tarandus L).

The effects of seasonal feeding on the structure and function of the hepatic microsomes of the reindeer were studied. In native microsomes the protein content did not vary depending on seasonal feeding, but there was a slight modification of the lipid moiety. The sensitivity of microsomes to membrane treatments changed from season to season. Seasonal feeding did not affect the hepatic cytochrome c reductase activity. However, the poor winter food depressed UDPglucuronosyltransferase activity to one third of that after summer feeding. The UDPglucuronosyltransferase activity was lower in both native and treated microsomes. No differences were found in serum activities of aspartate or alanine aminotransferase although there were changes in the structure and function of hepatocytes. The poor winter feeding of the reindeer decreases their capacity to glucuronate foreign compounds and this is mediated by structural modification on the hepatic endoplasmic reticulum.