Plasma membrane calcium ATPase expression in the rat spinal cord.

Plasma membrane Ca2+-ATPase (PMCA) is a calcium pump that exists on the plasma membrane and has a role in keeping the intracellular Ca2+ concentration low. In the current study, the expression of PMCA isoforms in spinal cord tissues was investigated in detail and the changes of the expression was examined after contusion injury. Rats received a weight drop on the thoracic spinal cord as the injury or they received a sham surgery as a control. Three or twenty-four hours after spinal cord injury (SCI), the spinal cord was removed and processed for in situ hybridization, reverse transcription-polymerase chain reaction (RT-PCR) and immunohistochemistry. PMCA1-4 mRNAs were expressed in neurons in the control spinal cord. Each isoform of the PMCA proteins showed distinct expression patterns in the spinal cord. PMCA1 and PMCA3 were expressed in all of the layers of gray matter. PMCA2 was also abundant in gray matter, except laminae I and II, while PMCA4 expression was restricted to the superficial layers of the dorsal horn. Distinct expression patterns of the PMCA isoforms suggest differential functions of each isoform in the spinal cord. After spinal cord injury, the expression of PMCA2 was decreased; however, the change in expression of other isoforms showed a tendency of decrease but did not reach a statistically significant level. The decrease in PMCA expression may contribute to the increase in intracellular Ca2+ concentration and PMCA may have a role in secondary injury following spinal cord injury.