A fluorescent indicator for visualizing cAMP-induced phosphorylation in vivo

We have developed a method for visualizing phosphorylation of proteins in living cells using a novel fluorescent indicator composed of two green fluorescent protein (GFP) variants joined by the kinase-inducible domain (KID) of the transcription factor cyclic adenosine monophosphate (cAMP)-responsive element binding protein (CREB). Phosphorylation of KID by the cAMP-dependent protein kinase A (PKA) decreased the fluorescence resonance energy transfer (FRET) among the flanking GFPs. By transfecting COS-7 cells with an expression vector encoding this indicator protein (termed ART for cAMP-responsive tracer), we were able to visualize activation dynamics of PKA in living cells.

Antibody studies of factor VIII inhibitor in a case with Waldenström's macroglobulinemia

We report a case of Waldenström's macroglobulinemia with prominent bleeding tendency; laboratory investigation revealed an elevated activated partial thromboplastin time. Further laboratory evaluation showed circulating factor VIII anticoagulant, deemed polyclonal IgG, with a titer of 700 Bethesda Units/ml. The factor VIII inactivation kinetics of the patient plasma were identical to those of a type II inhibitor, and the inhibitor was found to recognize the A2 domain of the factor VIII heavy chain. Apparently, paraprotein is not always the cause of reduced activity of coagulation factors in neoplastic dysproteinemias.

Molecular basis of spatio-temporal dynamics in inositol 1,4,5-trisphosphate-mediated Ca2+ signalling

Inositol 1,4,5-trisphosphate (IP3)-mediated Ca2+ signalling regulates many important cell functions, and the spatio-temporal dynamics of the Ca2+ signalling is a crucial factor for its versatility. The molecular mechanisms that control Ca2+ signalling are now being investigated, and I here describe the subtypes of IP3 receptors that have distinct functional properties and contribute to the diversity of Ca2+ signalling patterns. I also discuss the spatio-temporal dynamics of intracellular IP3 concentration, describing recent methodological advances in monitoring intracellular IP3 concentration. These findings highlight the potential importance of the spatio-temporal information of any signalling molecule.

Histological evaluation of autogenous iliac particulate cancellous bone and marrow grafted to alveolar clefts--a preliminary report of five young adult cases

OBJECTIVE

We histologically evaluated iliac particulate cancellous bone and marrow (PCBM) grafted to alveolar clefts in five young adults with cleft lip and palate.

PATIENTS AND METHODS

Five young adults with cleft lip and palate underwent secondary alveolar bone grafting. The mean age of the patients was 21.2 years (range = 17 to 27 years). Bone specimens were taken from the graft site 5 to 10 months after the surgery simultaneously with implant fixture placement (two cases), vestibuloplasty (two cases), and rebone grafting (one case). These five bone specimens were prepared and stained with hematoxylin and eosin and examined microscopically.

RESULT

One specimen, taken 5 months after surgery, showed immature trabecular bone partially lined by osteoblasts. The remaining four specimens showed well-mineralized trabeculae and fatty change in the marrow space.

CONCLUSION

In young adult cases, PCBM remodeled after grafting and became mature bone about 5 to 6 months after the surgery.

[Analysis of segmental motor conduction in the median and the ulnar nerves: comparison between normal and diabetic individuals]

We investigated characteristics of segmental motor conduction in the median and the ulnar nerves. Subjects were 55 individuals with normal conduction of the upper extremity and 71 patients with diabetes mellitus. Mean polyneuropathy index (PNI), which was determined as a mean percentage of the normal for 6 indices concerning to the conduction velocity in the upper limb, was 99.0% in the normal group and 85.6 % in the diabetic group on the mean. In the normal group distal latency was longer in the median nerve than in the ulnar nerve, and the conduction time between Erb's point and the wrist was longer in the ulnar nerve than the median nerve both in men and women. In the diabetic group these differences were accentuated; that means the distal latency was relatively more prolonged in the median nerve and the conduction time between Erb's point and the wrist was much longer in the ulnar nerve. Prolonged distal latency in the median nerve of women and conduction delay between Erb's point and the wrist in the ulnar nerve of men altogether resulted in the gender difference in the median minus ulnar F-wave latency after wrist stimulation in the diabetic group. Carpal tunnel segment of the median nerve and the elbow segment of the ulnar nerve are known to be common entrapment sites. This phenomenon of accentuated conduction delay in these common entrapment sites might be considered as a sort of 'double crush syndrome'.

Dynamic Ca2+ signalling in rat arterial smooth muscle cells under the control of local renin-angiotensin system

1. We visualized the changes in intracellular Ca2+ concentration ([Ca2+]i), using fluo-3 as an indicator, in individual smooth muscle cells within intact rat tail artery preparations. 2. On average in about 45 % of the vascular smooth muscle cells we found spontaneous Ca2+ waves and oscillations ( approximately 0.13 Hz), which we refer to here as Ca2+ ripples because the peak amplitude of [Ca2+]i was about one-seventh of that of Ca2+ oscillations evoked by noradrenaline. 3. We also found another pattern of spontaneous Ca2+ transients often in groups of two to three cells. They were rarely observed and are referred to as Ca2+ flashes because their peak amplitude was nearly twice as large as that in noradrenaline-evoked responses. 4. Sympathetic nerve activity was not considered responsible for the Ca2+ ripples, and they were abolished by inhibitors of either the Ca2+ pump in the sarcoplasmic reticulum (cyclopiazonic acid) or phospholipase C (U-73122). 5. Both angiotensin antagonists ([Sar1,Ile8]-angiotensin II and losartan) and an angiotensin converting enzyme inhibitor (captopril) inhibited the Ca2+ ripples. 6. The extracellular Ca2+-dependent tension borne by unstimulated arterial rings was reduced by the angiotensin antagonist by approximately 50 %. 7. These results indicate that the Ca2+ ripples are generated via inositol 1,4, 5-trisphosphate-induced Ca2+ release from the intracellular Ca2+ stores in response to locally produced angiotensin II, which contributes to the maintenance of vascular tone.

[Inter-examiner reliability of nerve conduction measurements]

A total of 122 patients were performed motor and sensory nerve conduction studies of the upper limb by two examiners (1. doctor, 2. medical technician) to know the inter-examiner reliability of nerve conduction measurements. Subjects contained normal individuals and various types of neuropathy patients. Motor nerve conduction studies were carried out in the median nerve, and antidromic sensory nerve conduction studies were performed in the median and ulnar nerves. F-wave latency of the median nerve and sensory conduction velocity between finger and wrist of the median and ulnar nerves presented the equal mean value between two examiners. A relatively good correlation between two examiners was pointed out in the distal motor latency and F-wave latency. Inappropriate measurements were caused by the differences in the site of placement of stimulating or recording electrodes and effects of submaximum stimuli or stimulus spread to other nerves. In sensory nerve conduction studies, especially in the ulnar nerve, careful attention should be paid to avoid the influence of motor artifact in giving supramaximum stimuli. Amplitude measurements showed larger inter-examiner difference than latency or velocity measurements. We reported the present condition of measurement reliability. We should do our best to minimize the error.

Potentiating effects of 4-[2-(phenylsulfonylamino)ethylthio]-2,6-difluoro-phenoxyaceta mide (PEPA) on excitatory synaptic transmission in dentate granule cells

A novel sulfonylamino compound, 4-[2-(phenylsulfonylamino)-ethylthio]-2,6-difluoro-phenoxyaceta mide (PEPA) has been shown to selectively potentiate glutamate-induced currents in Xenopus oocytes expressing recombinant AMPA receptor subunits, GluR1-GluR4, by attenuation of desensitization. Here, we examined the effects of PEPA on responses to excitatory amino acids as well as on excitatory synaptic transmission in dentate granule cells of rat hippocampal slices using the whole-cell patch clamp technique. PEPA at 100 microM produced a 3-4-fold increases in the peak amplitude of current responses to AMPA and glutamate applied iontophoretically in the dentate granule cells, whereas it showed no effect on NMDA-induced currents. Excitatory postsynaptic currents (EPSCs) evoked in these neurons by stimulation of the perforant path had fast and slow components mediated by AMPA and NMDA receptors, respectively. PEPA at concentrations between 10 and 100 microM potentiated only the AMPA component of the EPSC (AMPA EPSC) in a dose-dependent manner without affecting the NMDA component. Although the potentiating effect of PEPA on the amplitude of the AMPA EPSC was weaker than that on the AMPA-induced current, it clearly prolonged the duration of the EPSC. PEPA at 100 microM increased the peak amplitude of the AMPA EPSC by 17%, and increased the area enclosed by the AMPA EPSC by 72%.

Three-dimensional CT imaging of aneurysm of aberrant right subclavian artery

We report a case of an aneurysm originating from an aberrant right subclavian artery, which was incidentally found as a compression deformity of the upper esophagus on a barium study in a 46-year-old man. Computed tomography (CT) clearly demonstrated the aneurysm of the aberrant right subclavian artery. In particular, reconstructed three-dimensional CT (3D-CT) was valuable in evaluating the positional relationships between the anomalous vessel with aneurysm and other structures.

[Interrelationship among nerve conduction velocity, amplitudes of compound muscle and compound nerve action potentials in diabetic neuropathy]

In order to clarify the relationship among amplitudes of compound nerve action potential (CNAP), compound muscle action potential (CMAP) and nerve conduction velocity parameters, data of nerve conduction studies were analyzed in 102 patients with diabetes mellitus. In motor conduction studies CMAP amplitudes after stimulations at the distal nerve trunk, and the polyneuropathy index (PNI), a mean percentage of normal for 12 indices from 4 nerves concerning to the velocity or long distance latency, were evaluated. CNAP was recorded in the median and ulnar nerves from an intrafascicularly inserted microelectrode at the elbow after wrist stimulation. CMAP amplitudes were high in the median and ulnar nerves, and were reduced in the tibial and peroneal nerves. A close relationship was found between PNI and CNAP amplitudes. Among CMAP amplitude parameters tibial nerve, not median or ulnar nerves, had a good correlation with PNI and CNAP amplitude. Along with the progression of diabetic neuropathy, neuropathic signs or symptoms become conspicuous, and nerve conduction velocity drops as is expressed by the PNI level, which reflects the change in nerve conduction velocity in the upper and lower limbs. At the same time CNAP amplitude or CMAP amplitude in the tibial nerve decreases, but in nerves of the upper limb CMAP amplitude doesn't always decrease. So, tibial nerve is best among CMAP amplitude parameters in evaluating the degree of diabetic neuropathy. It is necessary to judge the degree of diabetic neuropathy after due consideration of these facts.

Molecular aspects of the excitation-contraction coupling in skeletal muscle

Extremely rapid and massive release of Ca(2+) from the sarcoplasmic reticulum upon depolarization of the T-tubule regulates the contraction of skeletal muscle. The dihydropyridine receptor (voltage sensor) on the T-tubule faces the ryanodine receptor (Ca(2+) release channel) on the sarcoplasmic reticulum at the triadic junction and their intermolecular interaction is responsible for the swift release of Ca(2+) from the sarcoplasmic reticulum. We are now beginning to gain insight into the molecular structures that are important for the coupling mechanism.

[Effects of interelectrode separation in sensory nerve conduction studies]

Sensory nerve action potentials (SNAPs) obtained by conventional sensory nerve conduction studies are greatly influenced by the distance between exploring and reference electrodes. Changes in SNAPs were investigated in 12 healthy median nerves using the orthodromic and antidromic sensory nerve conduction studies with 1-cm, 2-cm, 3-cm, 4-cm, and 5-cm of interelectrode distances. Peak-to-peak (orthodromic) or baseline-to-peak (antidromic) amplitudes and durations between the positive peaks were measured and each value was expressed as a ratio to the recording of 1-cm of interelectrode distance. SNAPs with maximum amplitude were obtained by more than 3-cm of interelectrode distance. Duration of SNAP was increased by an increase of interelectrode distance. Change in amplitude along with the interelectrode distance was larger in the orthodromic method than in the antidromic method. Contrariwise, change in duration was larger in the antidromic method. SNAPs with long duration had a gently sloping configuration, and each peak tended to be indistinct. So, 3-cm of active and reference interelectrode separation should be recommended in performing sensory nerve conduction studies between wrist and finger, because maximum amplitude and clear visualization of peaks are available.

Synthesis and evaluation of 1-position-modified inositol 1,4,5-trisphosphate analogs

IP3 analogs were synthesized by the modification of phosphate at the 1-position, and their affinity for the IP3 receptor was analyzed by means of surface plasmon resonance measurements. Our results suggest that a hydrophobic and charged moiety linked to this position enhances the affinity for the IP3 receptor.

Case report: A case of lymphoepithelioma-like carcinoma of the oesophagus and review of the literature

A 78-year-old Japanese female was admitted to our hospital with dysphagia and weight loss. An oesophageal tumour was demonstrated radiologically and endoscopically, and was diagnosed as oesophageal cancer by biopsy. Histologically, the resected tumour showed poorly differentiated squamous cell carcinoma with prominent lymphoid stroma and was diagnosed as the so-called lymphoepithelioma-like carcinoma (LELC). Epstein-Barr virus in the tumour was negative by polymerase chain reaction and in situ hybridization. Oesophageal LELC is extremely rare. The cases in the literature, as well as the one reported here, presented with gross features of a submucosal tumour-like appearance. Although the differentiation of the tumour cells is often poor, prognosis seems to be better than for other types of oesophageal cancer. Oesophageal LELC has characteristic clinicopathological features and should be classified by criteria independent of other types of tumour.

Spatiotemporal dynamics of inositol 1,4,5-trisphosphate that underlies complex Ca2+ mobilization patterns

Inositol 1,4,5-trisphosphate (IP3) is a second messenger that elicits complex spatiotemporal patterns of calcium ion (Ca2+) mobilization and has essential roles in the regulation of many cellular functions. In Madin-Darby canine kidney epithelial cells, green fluorescent protein-tagged pleckstrin homology domain translocated from the plasma membrane to the cytoplasm in response to increased concentration of IP3. The detection of translocation enabled monitoring of IP3 concentration changes within single cells and revealed spatiotemporal dynamics in the concentration of IP3 synchronous with Ca2+ oscillations and intracellular and intercellular IP3 waves that accompanied Ca2+ waves. Such changes in IP3 concentration may be fundamental to Ca2+ signaling.

Expression of recombinant NMDA receptors in hippocampal neurons by adenoviral-mediated gene transfer

N-methyl-d-aspartate (NMDA) receptors have attracted a great deal of attention because they are intimately involved in brain development, synaptic plasticity and a variety of neurological disorders. The ability to artificially alter the properties of NMDA receptors in central nervous system (CNS) neurons would be useful for elucidating the physiological roles of these receptors. It would also raise the possibility of gene therapy of neurological diseases caused by malfunction of NMDA receptors. In this study, we constructed three recombinant adenoviruses encoding rat NMDA receptor subunit cDNAs, NMDAR1 (NR1), NMDAR2B (NR2B) and mutant NR1(N598R) in which the asparagine (N) site of the wild-type NR1 was replaced with arginine (R) by site-directed mutagenesis. PC12 cells co-infected with recombinant adenoviruses bearing NR1 and NR2B cDNAs expressed conventional NMDA receptors that were permeable to Ca2+ and sensitive to Mg2+, whereas those with viruses bearing NR1(N598R) and NR2B cDNAs expressed Ca2+-impermeable and Mg2+-insensitive receptors. When rat hippocampal neurons in culture were infected with NR1(N598R) and NR2B viruses, both Ca2+ permeability and Mg2+ sensitivity of NMDA receptors were markedly reduced in the infected neurons. Excitatory postsynaptic currents (EPSCs) mediated by NMDA receptors also became much less sensitive to Mg2+. Thus, the NR1(N598R)/NR2B receptors were more dominant than the native NMDA receptors in the infected neurons, and the former receptors introduced by the adenoviral vectors functioned as postsynaptic receptors. These results indicate that the functional properties of postsynaptic NMDA receptors can be manipulated by gene transfer technology using adenoviral vectors.

[Comparison of electrophysiological findings between CIDP and HMSN-1]

Chronic inflammatory demyelinating polyneuropathy (CIDP) and hereditary motor sensory neuropathy type 1 (HMSN-1) are representative myelinopathies. In order to differentiate changes in acquired and congenital demyelinating neuropathies, we studied electrophysiologically 9 patients with active phase of CIDP (36.0 +/- 17.6 years old; mean +/- SD) and 7 patients with genetically-proven HMSN-1 A (56.0 +/- 13.6 years old). Motor conduction studies demonstrated longitudinal uniformity in HMSN-1, contrariwise focal conduction block or conduction delay in CIDP. The mean median nerve conduction velocity in the forearm segment and the mean CMAP amplitude stimulated at the wrist were not different between CIDP and HMSN-1 group; 31.8 +/- 7.2 m/sec and 5.6 +/- 2.8 mV in CIDP, and 26.7 +/- 9.8 m/sec and 3.2 +/- 2.6 mV in HMSN-1, respectively. Upper extremity polyneuropathy index (PNI), a mean percentage of normal for 6 indices concerning to the velocity and latency over two nerves obtained by motor conduction studies, was equal and around 50% on the average in each group. Conduction blocks were presented in 7 patients with CIDP and only one patient with HMSN-1. No sensory nerve action potential was recorded in 6 out of 9 patients with CIDP, and in 6 out of 7 patients with HMSN-1. Intrafascicular neurography of the median nerve, stimulated at the wrist and recorded from intrafascicularly inserted microelectrode at the elbow, revealed irregular multiphasic waves which signify severe temporal dispersion. Maximum conduction velocity was similarly reduced to 48 m/sec in CIDP and 44 m/sec in HMSN-1 on the average, but in one patient with HMSN-1 it was maintained to 63 m/sec with conspicuous temporal dispersion of the waveform. Amplitude of the compound nerve action potential (CNAP) decreased more (p < 0.01) in HMSN-1 (26 +/- 11 micro V) than in CIDP (72 +/- 25 micro V). Temporal dispersion of CNAP was prominent in HMSN-1 than in CIDP. In conclusion, electrophysiological changes were more homogeneous in the longitudinal distribution but more heterogeneous in the cross-sectional distribution in HMSN-1 than in CIDP.

[Radiographic diagnosis of cardiogenic pulmonary edema]

Development of pulmonary edema (increased extravascular lung water) is a common and sometimes life-threatening clinical problem in critical-care unit patients. There are three principal causes: cardiac failure, overhydration, and increased pulmonary capillary permeability. Among these, cardiogenic edema consists of left heart failure and overhydration. Determining the specific cause of any given case of pulmonary edema is important and leads to more rapid and definitive treatment. A plain chest film can often explicate the cause of edema with a high degree of accuracy if careful attention is given to certain radiographic features. The principal features useful for correctly determining the cause of edema in a high percentage of cases are the distribution of pulmonary blood flow, distribution of pulmonary edema, and vascular pedicle width. Ancillary features are pulmonary blood volume, bronchial cuffing, septal lines, pleural effusion, and air bronchograms. Cardiac size and shape as well as specific intracardiac calcifications could also help distinguish cardiogenic from noncardiogenic pulmonary edema.

Inhibitory modulation of B cell receptor-mediated Ca2+ mobilization by Src homology 2 domain-containing inositol 5'-phosphatase (SHIP)

Src homology 2 domain-containing inositol 5'-phosphatase (SHIP) mediates inhibitory signals that attenuate intracellular Ca2+ mobilization in B cells upon B cell receptor (BCR) stimulation. To clarify the mechanisms affected by SHIP, we analyzed Ca2+ mobilization in the DT40 B cell line in which the SHIP gene was disrupted. In SHIP-deficient cells, Ca2+ transient elicited by BCR stimulation was more prolonged than that in control cells both in the presence and absence of extracellular Ca2+. Inositol 1,4, 5-trisphosphate production following BCR stimulation was enhanced in SHIP-deficient cells. In SHIP-deficient cells in comparison with the control cells, BCR stimulation in the absence of extracellular Ca2+ induced a greater degree of Ca2+ store depletion and the Ca2+ influx upon re-addition of extracellular Ca2+ was also greater. However, store-operated Ca2+ influx (SOC) elicited by thapsigargin-induced store depletion was not affected by SHIP. These results indicate that the primary target pathway of SHIP is the Ca2+ release from the stores, and that Ca2+ influx by the SOC mechanism is secondarily controlled by the level of Ca2+ in the stores without direct inhibition of SOC. In this way, SHIP may play an important role in ensuring the robust tuning of Ca2+ signaling in B cells.

[Superiority of intrafascicular neurography over conventional nerve conduction studies in evaluating axonal degeneration]

We investigated conventional motor and sensory nerve conduction studies (MCS & SCS) with regard to the sensitivity in detecting axonopathies. Twelve patients with axonal type of polyneuropathy, 2 vincristin neuropathy and 10 cisplatin neuropathy, were examined by MCS & SCS. Their data were compared with those by intrafascicular microneurography (MNG) of the median nerve. Nerve conduction velocities were within normal limits or slightly reduced to 87-99% of the normal. Amplitude of compound muscle action potential (CMAP) by MCS decreased to 4 or 5 mV in vincristin neuropathy, though cisplatin neuropathy presented normal amplitude. Amplitude of sensory nerve action potential (SNAP) by SCS was undetected in one median nerve and in three sural nerves. While, compound nerve action potential (CNAP) by MNG was all recorded, and presented the amplitude value of below 150 microV in seven patients. The waveform was normal or mild neuropathic pattern. No patients presented normal CNAP amplitude and reduced SNAP amplitude. But there were three patients who had normal SNAP amplitude and reduced CNAP amplitude. In SCS we could recognize abnormal only after CNAP amplitude by MNG dropped to below 100 microV. Cisplatin neuropathy demonstrates reduction of CNAP or SNAP amplitude, and vincristin neuropathy further presents reduction of CMAP amplitude. Evaluation of axonopathy is best achieved by nerve action potential amplitude. Conventional surface electrode methods are available for this purpose, but MNG is more sensitive and is capable of quantitative analysis even in severely damaged nerves.

Postsynaptic expression of Ca2+-permeable AMPA-type glutamate receptor channels by viral-mediated gene transfer

The ability to artificially express a particular receptor protein in the postsynaptic sites of neurons in the central nervous system (CNS) would be useful for the study of synaptic function of cloned receptor genes as well as for gene therapy of neurological disorders caused by dysfunction of postsynaptic receptors. In this study, we aimed to express the cDNA of unedited GluR2 subunit of the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)-type glutamate receptor that forms inwardly rectifying and Ca2+-permeable channel in CNS neurons by using adenoviral-mediated gene transfer. For this purpose, we have constructed a recombinant adenovirus bearing an expression-switching unit, where the unedited GluR2 cDNA can be activated by the Cre recombinase-mediated excisional deletion of a stuffer DNA interposed between the promotor and the coding region. When PC12 cells were infected with this recombinant adenovirus together with an adenovirus expressing Cre recombinase, the inwardly rectifying and Ca2+-permeable AMPA receptor channels were expressed in nearly 100% of infected cells. Two days after co-infection of cultured rat hippocampal neurons with these adenoviruses, fast excitatory neurotransmission in the glutamatergic synapse was mediated predominantly by the inwardly rectifying and Ca2+-permeable AMPA receptor channels. This indicates that the native AMPA receptors in the postsynaptic sites of the glutamatergic synapse are replaced rapidly with recombinant receptors newly produced by the viral-mediated gene transfer.

Encoding of Ca2+ signals by differential expression of IP3 receptor subtypes

Inositol 1,4,5-trisphosphate (IP3) plays a key role in Ca2+ signalling, which exhibits a variety of spatio-temporal patterns that control important cell functions. Multiple subtypes of IP3 receptors (IP3R-1, -2 and -3) are expressed in a tissue- and development-specific manner and form heterotetrameric channels through which stored Ca2+ is released, but the physiological significance of the differential expression of IP3R subtypes is not known. We have studied the Ca2+-signalling mechanism in genetically engineered B cells that express either a single or a combination of IP3R subtypes, and show that Ca2+-signalling patterns depend on the IP3R subtypes, which differ significantly in their response to agonists, i.e. IP3, Ca2+ and ATP. IP3R-2 is the most sensitive to IP3 and is required for the long lasting, regular Ca2+ oscillations that occur upon activation of B-cell receptors. IP3R-1 is highly sensitive to ATP and mediates less regular Ca2+ oscillations. IP3R-3 is the least sensitive to IP3 and Ca2+, and tends to generate monophasic Ca2+ transients. Furthermore, we show for the first time functional interactions between coexpressed subtypes. Our results demonstrate that differential expression of IP3R subtypes helps to encode IP3-mediated Ca2+ signalling.

Critical duration of intracellular Ca2+ response required for continuous translocation and activation of cytosolic phospholipase A2

When cells are exposed to certain external stimuli, arachidonic acid (AA) is released from the membrane and serves as a precursor of various types of eicosanoids. A Ca2+-regulated cytosolic phospholipase A2 (cPLA2) plays a dominant role in the release of AA. To closely examine the relation between Ca2+ response and AA release by stimulation of G protein-coupled receptors, we established several lines of Chinese hamster ovary cells expressing platelet-activating factor receptor or leukotriene B4 receptor. Measurement of intracellular Ca2+ concentration ([Ca2+]i) demonstrated that cell lines capable of releasing AA elicited a sustained [Ca2+]i increase when stimulated by agonists. The prolonged [Ca2+]i elevation is the result of Ca2+ entry, because this elevation was blocked by EGTA treatment or in the presence of Ca2+ channel blockers (SKF 96365 and methoxyverapamil). cPLA2 fused with a green fluorescent protein (cPLA2-GFP) translocated from the cytosol to the perinuclear region in response to increases in [Ca2+]i. When EGTA was added shortly after [Ca2+]i increase, the cPLA2-GFP returned to the cytosol, without liberating AA. After a prolonged [Ca2+]i increase, even by EGTA treatment, the enzyme was not readily redistributed to the cytosol. Thus, we propose that a critical time length of [Ca2+]i elevation is required for continuous membrane localization and full activation of cPLA2.