Potassium and calcium changes in injured spinal cords

Area of Science:

• Neuroscience
• Spinal Cord Injury Research
• Biochemistry

Background:

• Previous studies noted significant extracellular potassium ([K+]e) rises and calcium ([Ca2+]e) falls in injured spinal cords.
• Observed rapid [K+]e recovery but persistent [Ca2+]e depression suggested diffusion block or a calcium sink.

Purpose of the Study:

• To investigate the spatial distribution of tissue potassium ([K]t) and calcium ([Ca]t) concentrations in injured cat spinal cords.
• To resolve discrepancies in extracellular ion recovery patterns following spinal cord contusion.

Main Methods:

• Utilized atomic absorption spectroscopy to measure [K]t and [Ca]t.
• Compared injured cat spinal cords with uninjured controls following standardized contusion.

Main Results:

• [K]t decreased significantly at the impact site (51% and 35% of control at 1 and 3 h), with surrounding cord gaining potassium.
• [Ca]t increased significantly at the impact site (37% and 59% above control at 1 and 3 h), with surrounding cord losing calcium.
• Potassium loss suggests >80% cell disruption; calcium gain indicates influx from surrounding tissue.

Conclusions:

• Spinal cord contusion causes substantial cell disruption and potassium efflux from the impact site.
• Calcium accumulation at the impact site originates from surrounding cord tissue.
• Inorganic phosphate sequestration likely forms a deep calcium sink at the injury site.