Serum lipids, thyroxine and catecholamine levels in the reindeer with reference to the annual climatic cycle

Abstract

1. 1. Blood glucose and lactate, serum total lipid and triglyceride, thyroxine (T 4), epinephrine and norepinephrine concentrations and serum dopamine-β-hydroxylase activity were studied in 76 reindeer hinds and 127 calves with reference to the seasons. 2. 2. Blood glucose level tended to be lowest in Autumn, and blood lactate highest in Summer. 3. 3. Serum total lipids were smallest in Spring (2.8 g/l) and greatest in Autumn (5.3 g/l). Triglycerides were smallest in Winter (0.18 mmol/l) and highest in Autumn (0.32 mmol/l). In calves the total lipids increased during the neonatal period. 4. 4. Serum epinephrine correlated with the weight, age, blood glucose and total lipids of the animals. In adult animals the lowest serum epinephrine level was found in Spring and the highest in Autumn (55 vs 190 ng/ml). 5. 5. Serum norepinephrine concentration and dopamine-β-hydroxylase activity were highest in Spring and decreased towards Autumn. Parturition affected these parameters significantly. 6. 6. The preponderance of high levels of some blood constituents in Autumn may be attributable to the replenishment of energy supplies for Winter time and also to the rutting season. 7. 7. T 4 was smallest in Spring and highest in Summer. It was slightly greater in Winter than in Autumn. This suggests that the metabolic rate is tower in Winter than in Summer. Thus, the adaptation of the reindeer to a cold climate mainly utilizes insulation.