Hibernation and disuse osteoporosis

Abstract

In an attempt to determine 1) if disuse osteoporosis occurs naturally during hibernation and 2) if it can be induced by limb immobilization in active and hibernating ground squirrels, forty-six thirteenlined ground squirrels were divided into five experimental groups. Group one was the active control group (AC) (ten animals). Group two was the active immobilized (AI) group and was subjected to a unilateral sciatic nerve section (ten animals). Group three was the hibernating control group and was allowed to hibernate undisturbed for 30 days (HC) (ten animals). The fourth group was subjected to a unilateral sciatic nerve section and allowed to hibernate for 30 days; this was the hibernating immobilized group (HI). The fifth group of six animals received the identical treatment as the (HI) group but was allowed to hibernate for 150 days. The following measurements were taken: Gastrocnemius-soleus mass, body mass, tibia-fibula weight, total tibia-fibula calcium and phosphorus. In addition, the femur was observed histologically for the enlarged lacunae typical of osteoporotic bone. Statistical analysis was accomplished with the Wilcoxan sign rank test. The data were interpreted to mean: 1) Disuse osteoporosis can be induced in active ground squirrels, 2) disue osteoporosis is not evident nor can it be induced by limb immobilization during 30 days of hibernation and 3) limb immobilization did not result in significant disuse osteoporosis following 150 days of hibernation. Only a few enlarged lacunae were evident after 150 days of hibernation.