Rapid changes in creatine phosphate level in cerebral cortex slices

Abstract

Rapid changes in the creatine phosphate and inorganic phosphate levels in slices of cerebral cortex during the passage of electrical pulses were studied in a phosphate-free medium, buffered with aminotris-hydroxymethylmethane. On passage of pulses, creatine phosphate was broken down at a rate of 1400[mu] moles/g wet weight tissue/hours, after an initial lag period of 2-3 seconds. Breakdown was complete in 5 seconds. The breakdown was preceded by a slight fall in the level of ATP, which regained its original value when creatine phosphate breakdown commenced. If the pulses were switched off within 7 seconds of application, creatine phosphate was resynthesized to the original level within 20 seconds. The rate of resynthesis was 150[mu] moles/g wet weight tissue/hour and was almost linear with time. After prolonged passage of pulses creatine phosphate was resynthesized only after 90 seconds. This resynthesis took place more rapidly towards the end of this period than at the beginning. Treatment of slices of cerebral cortex with 0.09 [image] KCl decreased the creatine phosphate level within 60 seconds to a level similar to that produced by electrical pulses in 5 seconds. The changes in level of inorganic phosphate in the slices, under the above conditions, mirrored the changes in creatine phosphate levels, with the exception of slices treated with excess of KC1. In this case, the inorganic phosphate level did not rise until the creatine phosphate level had fallen by 80% of the total decrease.