Kaname Ohyama1, Yuka Ikeshita2, Yuki Fuchigami3, Shigeru Kawakami3, Mihoko N Nakashima4, Mikiro Nakashima5. 1. Unit of Medical Pharmacy, Department of Pharmacy Practice, Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki, Japan. Electronic address: k-ohyama@nagasaki-u.ac.jp. 2. School of Pharmaceutical Sciences, Nagasaki University, Nagasaki, Japan. 3. Department of Pharmaceutical Informatics, Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki, Japan. 4. Division of Clinical Pharmacy, Faculty of Pharmaceutical Sciences, Sojo University, Kumamoto, Japan. 5. Unit of Medical Pharmacy, Department of Pharmacy Practice, Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki, Japan.
Abstract
BACKGROUND: Microdialysis (MD) is conventionally used to measure the in vivo levels of various substances and metabolites in extracellular and cerebrospinal fluid of brain. However, insertion of the MD probe and subsequent perfusion to obtain samples cause damage in the vicinity of the insertion site, raising questions regarding the validity of the measurements. NEW METHOD: We used fluorogenic derivatization liquid chromatography-tandem mass spectrometry, that quantifies both high and low abundance proteins, to differentiate the effects of perfusion from the effects of probe insertion on the proteomic profiles of expressed proteins in rat brain. RESULTS: We found that the expression levels of five proteins were significantly lower in the perfusion group than in the non-perfusion group. Three of these proteins are directly involved in ATP synthesis. In contrast to decreased levels of the three proteins involved in ATP synthesis, ATP assays show that perfusion, following probe insertion, even for a short time (3 h) increased ATP level up to 148% that prior to perfusion, and returned it to normal state (before probe insertion). COMPARISON WITH EXISTING METHOD: There is essentially no information regarding which observed changes are due to probe insertion and which to perfusion. CONCLUSIONS: Our findings partially demonstrate that the influence of whole MD sampling process may not significantly compromise brain function and subsequent analytical results may have physiological equivalence to normal, although energy production is transiently damaged by probe insertion.
BACKGROUND: Microdialysis (MD) is conventionally used to measure the in vivo levels of various substances and metabolites in extracellular and cerebrospinal fluid of brain. However, insertion of the MD probe and subsequent perfusion to obtain samples cause damage in the vicinity of the insertion site, raising questions regarding the validity of the measurements. NEW METHOD: We used fluorogenic derivatization liquid chromatography-tandem mass spectrometry, that quantifies both high and low abundance proteins, to differentiate the effects of perfusion from the effects of probe insertion on the proteomic profiles of expressed proteins in rat brain. RESULTS: We found that the expression levels of five proteins were significantly lower in the perfusion group than in the non-perfusion group. Three of these proteins are directly involved in ATP synthesis. In contrast to decreased levels of the three proteins involved in ATP synthesis, ATP assays show that perfusion, following probe insertion, even for a short time (3 h) increased ATP level up to 148% that prior to perfusion, and returned it to normal state (before probe insertion). COMPARISON WITH EXISTING METHOD: There is essentially no information regarding which observed changes are due to probe insertion and which to perfusion. CONCLUSIONS: Our findings partially demonstrate that the influence of whole MD sampling process may not significantly compromise brain function and subsequent analytical results may have physiological equivalence to normal, although energy production is transiently damaged by probe insertion.