DISTRIBUTION OF ALPHA-1 SUBUNIT ISOFORM OF (NA,K)-ATPASE IN THE RAT SPINAL-CORD

Three isoforms of the alpha subunit of (Na,K)-ATPase have been identif ied in the rat central nervous system. Using a probe specific for the alpha 1 isoform, mRNA levels were measured from five sections of the r at spinal cord using slot blot techniques. Assigning a value of 1 to t he slope obtained from the cervical section, the upper thoracic sectio n was 2.6 times higher; the midthoracic section was 4.5 times higher; the lower thoracic section was 2.6 times higher; and the lumbar sectio n was 1.7 times higher. The results suggest that alpha 1 isoform mRNA levels are not uniform throughout the spinal cord. In situ hybridizati on techniques showed that alpha 1 isoform mRNA was diffusely abundant in glial and central canal ependymal cells, while labeled neurons were localized exclusively in laterally located anterior horn neurons in c ervical, thoracic, and lumbar segments and in ventromedial neurons in mid-thoracic spinal cord. Also, dorsal root ganglia neurons were exten sively labeled at all segments.