Brain intracellular

Kato, T., Murashita, J., Kamiya, A., Shioiri, T, Kato, N., and Inubushi, T. (1998) Decreased brain intracellular pH measured by 31P-MRS in bipolar disorder a confirmation in drug-free patients and correlation with white matter hyperintensity. Eur Arch Psychiatry Clin Neurosci, 248 301—306. 

Brain intracellular pH level lower acidity —> higher (0.63). 

II Phosphatidic acid- Testis, brain Intracellular 98 kDa PA, PE Catalytic center 16... 

Active Transport. Maintenance of the appropriate concentrations of K" and Na" in the intra- and extracellular fluids involves active transport, ie, a process requiring energy (53). Sodium ion in the extracellular fluid (0.136—0.145 AfNa" ) diffuses passively and continuously into the intracellular fluid (<0.01 M Na" ) and must be removed. This sodium ion is pumped from the intracellular to the extracellular fluid, while K" is pumped from the extracellular (ca 0.004 M K" ) to the intracellular fluid (ca 0.14 M K" ) (53—55). The energy for these processes is provided by hydrolysis of adenosine triphosphate (ATP) and requires the enzyme Na" -K" ATPase, a membrane-bound enzyme which is widely distributed in the body. In some cells, eg, brain and kidney, 60—70 wt % of the ATP is used to maintain the required Na" -K" distribution. 

The intracellular pH can also regulate the exchanger. [H+] strongly inhibits NCX activity under steady-state conditions, in fact, reduction in [pH] values, as little as 0.4, can induce a 90% inhibition of NCX activity. Such inhibitory action depends on the presence of intracellular Na+ ions, hence, the action exerted by H+ ions is pathophysiologically relevant with regards to brain and heart ischemia. 

Acute over-activation of NHE1 results in a marked elevation in intracellular sodium concentration with a subsequent increase in intracellular calcium, via the Na +/Ca++ exchanger. This in turn triggers a cascade of injurious events that can culminate in tissue dysfunction and ultimately apoptosis and necrosis. This is commonly seen in organs such as the heart, brain and kidneys as a consequence of ischemia-reperfusion. 

Because of their strategic localization, astrocytes play a crucial role in maintaining the extracellular ionic homeostasis, provide energetic metabolites to neurons and remove excess of neurotransmitter in schedule with synaptic activity. In addition, the strategic location of astrocytes allows them to carefully monitor and control the level of synaptic activity. Indeed, number of papers during the last 15 years have shown that cultured astrocytes can respond to a variety of neurotransmitters with a variety of different patterns of intracellular calcium increases (Verkhratsky et al. 1998). Later on, studies performed in intact tissue preparations (acute brain slices) further established that the plasma membrane receptors can sense external inputs (such as the spillover of neurotransmitters during intense synaptic activity) and transduce them as intracellular calcium elevations, mostly via release of calcium from internal stores (Dani et al. 1992 Murphy et al. 1993 Porter and McCarthy... 

Sharp BM (2003) Opioid receptor expression and intracellular signaling by cells involved in host defense and immunity. Adv Exp Med Biol 521 98-105 Sharp BM (2006) Multiple opioid receptors on immune cells modulate intracellular signaling. Brain Behav Immun 20 9-14... 

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