Early onset of disk degeneration and spondylosis in sand rats (Psammomys obesus).

The sand rat is a desert animal which feeds mainly on salt bush, a shrub with a high salt content in its leaves. Sand rats have been used for the study of renal function, and since they may develop diabetes if kept on a laboratory diet without a supplement of salt bush, they have been used for investigation of diabetes-related disorders as well. Older diabetic and non-diabetic sand rats are prone to develop severe degeneration of the intervertebral disks, disk herniation, and subsequent hyperostotic spondylosis. This report is concerned with the relation of these processes to aging. The vertebral columns of 25 sand rats which were fed a standard laboratory diet and a supplement of salt bush ad libitum were examined. The sand rats ranged from 12 to 18 months of age. The vertebral columns were dissected, prepared for microscopic examination, and the findings were compared with those obtained previously in sand rats from 1 1/2 to 2 1/2 years of age. Both disk degeneration and spondylosis were comparable in course and frequency to the changes found in the older sand rats. It was concluded that factors other than age are involved in the pathogenesis of disk degeneration in the sand rat.