Biomedical subjects

N Hagiwara

Publications and source records attributed to N Hagiwara.

At least 55 records · Page 3Linked to original sources

PubMed1996

Neurogenesis and cell death in olfactory epithelium.

The olfactory epithelium (OE) of the mammal is uniquely suited as a model system for studying how neurogenesis and cell death interact to regulate neuron number during development and regeneration. To identify factors regulating neurogenesis and neuronal death in the OE, and to determine the mechanisms by which these factors act, investigators studied OE using two major experimental paradigms: tissue culture of OE; and ablation of the olfactory bulb or severing the olfactory nerve in adult animals, procedures that induce cell death and a subsequent surge of neurogenesis in the OE in vivo. These studies characterized the cellular stages in the olfactory receptor neuron (ORN) lineage, leading to the realization that at least three distinct stages of proliferating neuronal precursor cells are employed in generating ORNs. The identification of a number of factors that act to regulate proliferation and survival of ORNs and their precursors suggests that these multiple developmental stages may serve as control points at which cell number is regulated by extrinsic factors. In vivo surgical studies, which have shown that all cell types in the neuronal lineage of the OE undergo apoptotic cell death, support this idea. These studies, and the possible coregulation of neuronal birth and apoptosis in the OE, are discussed.

Animals↗

PubMed1996

Enhancement of the L-type Ca2+ current by mechanical stimulation in single rabbit cardiac myocytes.

Anion conductance is known to be activated by mechanical stimulation, such as osmotic cell swelling or cell inflation via the patch pipette, of canine or rabbit cardiac myocytes. The effects of mechanical stimulation on time-dependent currents, however, remain unsettled. Using the whole-cell voltage-clamp method, we have found that mechanical stimuli enhance the L-type Ca2+ current (ICa,L) in rabbit cardiac myocytes. At every membrane potential, ICa,L was reversibly increased by osmotic cell swelling and by cell inflation caused by applying a positive pressure of 10 to 15 cm H2O via the patch pipette. ICa,L was increased during cell inflation by 37 +/- 21% (mean +/- SD, n = 17) in atrial cells and by 37 +/ -8% (n = 7) in sinoatrial node cells in solution containing 2 mmol/L Ca2+. The current-voltage relationship, the inactivation time constant, the steady state inactivation curve, and the conductance properties of ICa,L were all virtually unaffected by mechanical stimulation except for the open probability, which appears to increase. The increase in ICa,L was not dependent on protein kinase A, since an inhibitor peptide of cAMP-dependent protein kinase failed to prevent the increase in ICa,L during mechanical stimuli (n=5). The increase in ICa,L caused by cell inflation was unaffected by the chelation of intracellular Ca2+ by the addition of 10 mmol/L EGTA or 10 mmol/L BAPTA to the pipette solution, suggesting that the effect was not mediated by changes in intracellular Ca2+. Thus, mechanical stimulation due to cell swelling or inflation may itself directly increase ICa,L in rabbit cardiac myocytes.

Animals↗

PubMed1995

Regulation of the rat S100 beta gene expression: the role of the 2 kb 5'-upstream sequence in glial specific expression.

We have studied the role of the 2047 bp 5'-upstream region and 232 bp first exon sequence of the rat S100 beta gene in glial specific expression. S100 beta luciferase expression vectors carrying serial deletions of the S100 beta 5' upstream sequence were constructed and transiently transfected into the peripheral nervous system (PNS) glial-type cell line RT4-D6, the PNS neuronal-type cell line RT4-E5, and the central nervous system (CNS) glial-type cell line C6. The hepatoma cell line HTC was also transfected as a nonneural control. From this functional analysis, we found a glial-specific positive regulatory sequence(s) mapped between -583 and -106 relative to the transcriptional start site. This region confers a significantly higher level of luciferase expression in the glial-type cell lines RT4-D6 and C6 than in the neuronal cell line RT4-E5 and the hepatoma cell line HTC. Also, a non-cell type specific positive regulatory element was identified in the first exon sequence between +78 and +232. Though non-cell type-specific, it was found to have a predominant effect in glial cells. From these observations, we have concluded that the 2047 bp 5'-upstream region and 232 bp of the first exon sequence confers the high levels of S100 beta expression in glial cells through these two positive elements.

Animals↗

PubMed1995

Chloride conductance in human atrial cells.

Many types of chloride current have been reported in the hearts of various species; however, the nature of chloride conductance in the human heart is still unclear. We investigated cyclic AMP-dependent chloride current and swelling-induced chloride current in isolated human atrial cells using the whole-cell voltage-clamp method. External application of 1 microM isoprenaline increased calcium current by 391.9 +/- 48.6% (mean +/- S.D., n = 8); however, there was no activation of cyclic AMP-dependent chloride current at steady-state membrane potentials between -80 and +50 mV. Neither external application of 10 microM forskolin nor internal application of 50 microM cyclic AMP activated a cyclic AMP-dependent chloride current. On the other hand, when the same cell was superfused with a 50% hypotonic solution, it exhibited osmotic swelling and an outward rectifying current (6.59 +/- 0.96 pA/pF at +30 mV, n = 10). This swelling-induced current reversed at -26.5 +/- 3.1 mV (n = 10), close to the calculated equilibrium potential for chloride, and it was sensitive to the stilbene-derivative chloride channel blocker. In conclusion, no activation of cyclic AMP-dependent chloride current was observed in human atrial cells. On the other hand, a swelling-induced chloride current was consistently demonstrated and its kinetic properties were similar to those reported in other cardiac myocytes.

4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfo↗

PubMed1995

Proximal tubular cell alkalinization induced by Na(+)-glucose cotransport.

To study the ionic mechanisms of crosstalk between luminal and peritubular membranes induced by Na(+)-glucose cotransport in the proximal tubular cells, we applied the ion-selective microelectrode techniques and measured intracellular ion activities of Na+ (Nai) and H+ (pHi), as well as peritubular membrane potential (EM) in doubly-perfused bullfrog kidney. In control conditions with peritubular HCO3- (15 mM), luminal perfusion with 10 mM D-glucose induced a 12 mV depolarization of peritubular membrane (glucose-induced depolarization) with a transient increase in Nai by 3 mM and an elevation in pHi by 0.1. In the absence of peritubular HCO3- (HEPES-Ringer at constant pH), the luminal glucose produced a sustained increase in Nai and suppression of pHi elevation without affecting glucose-induced depolarization. Peritubular perfusion with DIDS (10(-4) M) abolished the change in pHi induced by luminal glucose. Furthermore, the luminal glucose increased the transport number for K+ (gK/gm) in the peritubular membrane by 20%. These results suggest that 1) glucose-induced depolarization suppresses peritubular HCO3- exit, followed by an elevation in pHi, 2) the luminal glucose increases K+ conductance of the peritubular membrane, probably by the elevation in pHi, and 3) this increased K+ conductance repolarizes the peritubular membrane, which can support the driving force for Na(+)-glucose entry across the luminal membrane. Thus, we conclude that the crosstalk between peritubular and luminal membranes by Na(+)-glucose cotransport is mainly modulated by changes in cell pH and membrane potential in the proximal tubule.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗

PubMed1995

[Left diaphragmatic hernia due to blunt chest trauma complicated with intrapleural gastric perforation].

A 17-year-old male was injured by traffic accidents. Multiple left rib fractures, radiopacity of left hemithorax and rightward mediastinal shift lead us to the diagnosis of traumatic hemothorax. But left tube thoracostomy could not obtain any fluid. After this finding we suspected diaphragmatic hernia. Neither inserted nasogastric tube nor abdominal echogram could not lead to definitive diagnosis. Chest CT could identify stomach and spleen in the thoracic cavity. Insufflation of 300 ml air through nasogastric tube could not expand the stomach. By insertion of another thoracic tube some coffee-ground like materials could be obtained. Laparotomy disclosed rupture of left hemidiaphragm and intrathoracic displacement of the stomach and spleen. After reposition of stomach, we discovered 5 cm fissure of the stomach and left thoracic cavity filled with leaked gastric contents. Though reports of combined diaphragmatic hernia and gastric rupture are rare, these combination could occur if a patient with diaphragmatic hernia encounters blunt chest trauma on a full stomach.

Accidents, Traffic↗

PubMed1995

[Pharmacokinetic, bacteriological, and clinical studies on SY5555 in children].

Pharmacokinetic, bacteriological and clinical studies on SY5555 were performed in children. The results were as follows: 1. A total of 15 patients considered to have bacterial infections were treated with SY5555. Each dose, 5 mg/kg, was orally administered 3 times daily, for 4-11 days. Clinical efficacies of SY5555 in 13 patients with bacterial infections (1 with pneumonia, 2 with bronchitis, each 1 with maxillary sinusitis, 2 with otitis media, 5 with pharyngitis, 1 each with gastroenteritis and pyelonephritis) were evaluated as excellent in 10 patients and as good in 3 patients with an efficacy rate of 100%. Two patients with viral infection and malignant lymphoma were not evaluated. Thirteen causative strains in 7 species were found in 10 patients. Streptococcus pneumoniae in 1/3, Haemophilus influenzae in 2/2, Streptococcus pyogenes 4/4, Salmonella spp. in 1/1, Escherichia coli in 1/1 were eradicated. Only one patient developed mild diarrhea as an adverse reaction. Another patient showed elevated GPT (glutamate pyruvate transaminase). The abnormality was mild and the patient recovered after the cessation of SY5555 administration without specific treatment. 2. MICs of SY5555 were examined against 33 clinical isolates. SY5555 has low MICs against Enterococcus faecalis and other Gram-positive cocci. 3. Pharmacokinetic studies Peak plasma concentrations of SY5555 was 1.15 micrograms/ml at a dose level of 4.9 mg/kg orally administered at fasting. Based on the above results and the broad spectrum of the anti-bacterial activities, SY5555 appears to be a promising antibiotics that is usable as a single agent for the primary therapy of respiratory tract infections, skin soft tissue infections and urinary tract infections in children.

Bacterial Infections↗

PubMed1994

Glial-specific cAMP response of the glial fibrillary acidic protein gene cell lines.

Expression of the rat glial fibrillary acidic protein (GFAP) gene is responsive to the intracellular level of cAMP. We have examined the sequence 5'-upstream of the transcription start site of the rat GFAP-encoding gene to determine the elements responsible for regulating the cAMP response. The RT4 cell lines consist of a neural stem-cell type RT4-AC and its three derivative cell types, one glial-cell type, RT4-D, and two neuronal-cell types, RT4-B and RT4-E. GFAP is expressed in the stem-cell type and the glial-cell type but is not expressed in the neuronal-cell types. Luciferase expression vectors containing various areas of the 10.8-kb region upstream of the transcription start site of the GFAP gene were transiently transfected into these RT4 cells. The effect of cAMP was examined by quantitating the transient expression of luciferase. We found that (i) the 5'-upstream region alone (up to 10.8 kb) allows expression of the GFAP gene in the stem-cell type, the glial-cell type, and a neuronal-cell type; (ii) there are negative and positive cAMP-responsive elements that are juxtaposed within the region between -240 bp and -110 bp upstream and are functional in the stem-cell and glial-cell types but are not functional in the neuronal-cell type RT4-E; (iii) there may be elements that respond to dibutyryl-cAMP in all three RT4 cell types within the region from 2 kb to 10.8 kb upstream of the transcription start site; and (iv) a regulatory luciferase plasmid pRLgfap-1, containing both the upstream and downstream regulatory regions of the GFAP gene, not only expresses luciferase but also responds to forskolin in the stem-cell type and the glial-cell type. This regulatory plasmid, however, does not express in the neuronal-cell type with or without the forskolin treatment.

Animals↗

PubMed1994

Antidiuretic hormone-responding nonselective cation channel in distal nephron epithelium (A6).

Arginine vasotocin (AVT, 70 mU/ml) added from the basolateral side transiently activated a nonselective cation (NSC) channel with a single-channel conductance of 28.5 pS and almost identical selectivity for Na+ and K+ in the apical membrane of distal nephron cells (A6) cultured on permeable supports for 10-12 days in media containing 10% fetal bovine serum without supplemental aldosterone. The open probability (Po) of the NSC channel at the apical resting membrane potential in cell-attached patches was approximately 0.09 and increased when the apical membrane depolarized. The Po of the NSC channel was decreased by a rise in cytosolic Ca2+ concentration within a range of 30 nM-1 microM but not affected by cytosolic pH within a range of 6-8. The channel was activated by the application of negative pressure (10-60 cmH2O) into the patch pipette. Gadolinium (2 microM), an inhibitor of stretch-activated channels, decreased the Po by 40%. This blocking action of gadolinium was more effective after the channel was activated by stretch, i.e., 2 microM gadolinium decreased the Po by 70% when a negative pressure (60 cmH2O) was applied into the patch pipette. Amiloride (10 and 100 microM) showed a blocking action on the channel only when the NSC channel was activated by stretch.

Amiloride↗

PubMed1994

Functional significance of K+ and Cl- channels in volume regulation in proximal tubular cells.

Using the patch-clamp technique to cultured opossum kidney (OK) cells, we measured the activities of K+ channel and Cl- conductance during hyposmotic stress. The results are as follows: 1) A 50% lowered osmolarity of bath media induced a biphasic change of the membrane potential (EM): early hyperpolarization and late depolarization. The former transient response was abolished by removing Ca2+ from the cellular media, whereas the latter slow response was blocked by DIDS. 2) The hyposmosis-induced change of EM was due to K+ channels activated by cytosolic Ca2+. 3) In hyposmotic media, Cl- current was effectively increased, and this effect was abolished by Cl- channel blockers. 4) The hyposmosis-induced Cl- conductance was inhibited in the cytosolic acid media. In the alkaline media, it was enhanced even without hyposmotic stress. We conclude that the hyposmosis-induced activation of Cl- conductance, being stimulated by alkaline cell pH and inhibited by acid cell pH, may contribute to the ion transport and cell volume regulation along with the Ca(2+)-activated K+ channel.

Animals↗

PubMed1994

Role of pH-sensitive ion channels in regulation of cell volume in opossum kidney cells.

Applying the patch-clamp technique to cultured opossum kidney (OK) cells, we investigated effects of pH on the activation of Cl- channels induced by a hyposmotic shock. The Cl- conductance of cell membranes was measured in 145 mM NMG-Cl solution with the whole-cell configuration. Under control conditions, the Cl- conductance was almost negligible. When the cell was exposed to a hyposmotic medium, the Cl- conductance was remarkably elevated. This conductance change was reversibly inhibited by Cl- channel inhibitors, such as DIDS. The activation (pHi) from 7.3 to 7.0, but not influenced by changing the bath pH (pHe). We conclude that the Cl- channel activation by a hyposmotic challenge is highly sensitive to pHi.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗

PubMed1994

[Outpatient drainage treatment for simple spontaneous pneumothorax].

Spontaneous pneumothorax has been managed on an outpatient basis by intercostal tube drainage and a portable flutter valve device (pneumothorax set). In a series of 111 selected patients, from 14 to 75 years of age, who had no complaints such as dyspnea, had neither tension-nor hemo-pneumothorax, and could promptly return to hospital in an emergency, intercostal tube insertion and continuous negative pressure drainage were instituted at the outpatient department. After approximately one hour of suction, if an air leak ceased and the lung was re-expanded, the patient was allowed to return home with a pneumothorax set connected to the chest tube. But, if an air leak persisted, they were admitted to hospital. The outpatients were followed every 2 or 3 days thereafter, and if their course was uneventful, the chest tube was removed a week later. If the onset of lung recollapse was seen at outpatient check up, hospitalization was required. Outpatient treatment was successful in 81 cases (72.9%) of the series. However, 14 patients were hospitalized because of persistent air leak at the outpatient room, and 5 were admitted because of wound pain, re-expansion edema or other reasons. During the ambulatory course, 11 were admitted to hospital with recollapse of the lung. Bacterial cultures of drain tips were positive in 22.6% of 75 examined cases, which was a higher percentage than that associated with inpatient drainage. Wound infection with St. aureus occurred in one case after removal of the drain.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1994

[Pharmacokinetic, bacteriological and clinical studies on cefozopran in children].

Pharmacokinetic, bacteriological and clinical studies on cefozopran (CZOP) were performed in children. The results were as followed: 1. A total of 13 patients were treated with CZOP. The tested dose was 20 mg/kg (50 mg/kg in maxillary sinusitis), and the drug administered via intravenous bolus injection or 30-minute intravenous drip infusion 3 times daily, for 3-11 days. Clinical efficacies of CZOP in 13 patients with bacterial infections (11 with pneumonia, 1 with otitis media and 1 with maxillary sinusitis) were evaluated as excellent in 13 with an efficacy rate of 100%. Any adverse reactions or abnormal laboratory test results were not observed in any patients. Fourteen causative strains were found in 10 patients. Streptococcus pneumoniae in 4 cases out of 4, Streptococcus pyogenes in 1/1, Moraxella (Branhamella) catarrhalis in 3/3, Haemophilus influenzae in 4/6 were eradicated. 2. Pharmacokinetic studies. The mean serum concentration immediately after intravenous drip infusion over 30-minute of 20 mg/kg was 39.1 micrograms/ml (range: 25.6-52.5 micrograms/ml). The mean urinary recovery rate over 8 hours after administration was 49.0% (range: 45.2-51.8%). Based on the above results and the broad spectrum and great antibacterial activity of CZOP, it is considered that CZOP is a promising antibiotic usable as a single agent for the primary therapy of acute bacterial infections ranging from mild to severe in children.

Bacteria↗

PubMed1994

[Pharmacokinetic, bacteriological and clinical studies on biapenem (L-627) in children].

The results are summarized as follows: 1. A total of 10 patients were treated with biapenem (L-627). We received informed consent from all of their parents. Each dose was 6 mg/kg, and it was administered 3 times daily (40 mg/kg, 4 times daily in meningitis), in a 30-minute intravenous drip infusion for 5-17 days. The clinical efficacies of L-627 in 10 patients with bacterial infections (1 with purulent meningitis, 1 with sepsis, 5 with pneumonia, 2 with urinary tract infection and 1 with purulent tonsillitis) were evaluated as excellent in 8 patients, as good in 2 patients with an efficacy rate of 100%. Seven causative organisms found in 5 patients (Streptococcus pneumoniae in 2, Moraxella (Branhamella) catarrhalis in 2, Haemophilus influenzae in 2 and Pseudomonas aeruginosa in 1) were eradicated. No adverse reaction was observed in any of the 10 patients. 2. Pharmacokinetic studies Peak plasma concentrations of L-627 were 12.5-13.7 micrograms/ml at the dose of 6 mg/kg administered by 30-minute drip infusion. Plasma half-lives of L-627 in the beta-phase averaged 0.72 hour (0.63-0.80 hour). CSF concentration/plasma concentration ratios of L-627 were 1.12/8.16 micrograms/ml (Day 2, 1.17 hours after at dose of 20 mg/kg), 0.88/3.44 micrograms/ml (Day 3, 4.0 hours after at dose of 30 mg/kg) and 0.68/5.12 micrograms/ml (Day 13, 3.0 hours after at dose of 40 mg/kg) administered by 30-minute drip infusion in the child with purulent meningitis (case 1).(ABSTRACT TRUNCATED AT 250 WORDS)

Bacteria↗

PubMed1993

Cell-type specific segregation of transcriptional expression of glial genes in the rat peripheral neurotumor RT4 cell lines.

Four types of cells, RT4-AC (stem cell type), RT4-B and RT4-E (neuronal cell types), and RT4-D (glial cell type) were previously isolated from an ethylnitrosourea (ENU) induced rat peripheral neurotumor RT4. In a phenomenon termed cell-type conversion, RT4-AC spontaneously and permanently gives rise to the three other cell types in culture. In the RT4 system the expression of glial fibrillary acidic protein (GFAP) and S100 beta protein genes segregates in a cell-type specific manner. To further characterize the RT4 family, the expression of four myelin-forming glial genes--P0 glycoprotein, suppressed cAMP inducible POU (SCIP), 2',3'-cyclic nucleotide 3'-phosphodiesterase (CNP), and myelin basic protein (MBP)--has been studied in the RT4 cell lines. In addition to these genes, the expression of the low-affinity nerve growth factor (LNGF) receptor (expressed in immature Schwann cells) has been examined. We have found the following results. 1) The stem cell type RT4-AC and the glial cell type RT4-D express mRNA transcripts of P0, SCIP, and CNP (the larger form, 2.8 kb), and the amount of mRNA of these genes was increased by forskolin. 2) RT4-AC and RT4-D also express a low level of MBP mRNA upon forskolin treatment. 3) The neuronal cell types RT4-B and RT4-E do not express any of these myelin-forming glial genes with or without forskolin treatment. 4) The LNGF receptor mRNA is expressed in RT4-AC and RT4-D and at a lower level in RT4-B; its expression is stimulated by forskolin.

Animals↗

PubMed1993

Mechanisms of oxygen-induced contraction of ductus arteriosus isolated from the fetal rabbit.

The present study was designed to investigate the effect of O2 on intracellular Ca concentration ([Ca]i) in the ductus arteriosus and the mechanisms for O2-induced ductal contraction. The force of isometric contraction of the ring of the ductus arteriosus isolated from fetal rabbits at 30 days of gestation (term, 31 days) was measured. The ductus arteriosus was loaded with fura 2, a calcium-sensitive dye, and [Ca]i was determined from the ratio of fluorescence intensity at 340 and 380 nm excitation wavelengths. The ductus arteriosus was initially superfused with hypoxic control solutions and contraction was induced by application of oxygenated solutions. The O2-induced contraction of the ductus arteriosus was associated with increases in [Ca]i and was eliminated in the absence of extracellular calcium. An increase in [K]o from 5 to 50 mM, which causes membrane depolarization, induced ductal contraction. The calcium channel blockers verapamil, diltiazem, and nickel caused a similar inhibition of O2-induced contraction as well as KCl-induced contraction. The role of intracellular calcium stores in O2-induced ductal contraction was examined using ryanodine, an inhibitor of calcium uptake and release from the sarcoplasmic reticulum. The inhibition of O2-induced contraction by ryanodine was minimal. Infusion of glibenclamide, an inhibitor for opening the ATP-sensitive potassium channel, caused contraction of the ductus arteriosus in the hypoxic solution. Cromakalim, an opener of ATP-sensitive potassium channels, completely relaxed the contraction induced by O2. These data suggest that O2 increases [Ca]i and causes contraction in the ductus arteriosus. Application of O2 may change from anaerobic to aerobic metabolism and depolarize membrane potential by closing the ATP-sensitive potassium channel, which in turn increases calcium influx via the voltage-dependent calcium channel. Mechanisms other than the ATP-sensitive potassium channel may also be involved in the O2-induced contraction and remain to be studied.

Animals↗

PubMed1993

[Pharmacokinetic, bacteriological and clinical studies on S-1108 in children].

Pharmacokinetic, bacteriological and clinical studies on S-1108 were performed in children. The results were as follows: 1. A total of 11 patients were treated with S-1108. Each dose was 3 mg/kg, orally administered 3 times daily for 4-14 days. The clinical efficacies of S-1108 in 10 patients with bacterial infections (1 with bacteremia, 4 with pneumonia, 1 with acute maxillary sinusitis, 1 with scarlet fever and 2 with streptococcal pharyngitis) were evaluated as excellent in 8 patients and as good in 2 patients with an efficacy rate of 100%. Only one patient with staphylococcal scalded skin syndrome due to methicillin resistant Staphylococcus aureus (MRSA) who received gamma-globulin was not evaluated. Fourteen causative strains of 5 species were found in 10 patients. Three strains of Streptococcus pneumoniae out of 5, 2 of 3 Branhamella catarrhalis strains, none of Staphylococcus aureus and all 3 strains of Streptococcus pyogenes were eradicated. No adverse reaction was observed in any of the 11 patients. 2. MICs of S-1108 against 5 clinically isolated S. pneumoniae from cases of infections were examined. All of them were relatively highly resistant to penicillins. S-1108 was compared with cefteram pivoxil, cefpodoxime proxetil, cefaclor and cefixime, and it showed better antibacterial activity or than other cephems. 3. Double peaks were obtained in plasma levels of S-1108 orally administered at a dose of 3 mg/kg at 30 minutes after meal and were 1.03 microgram/ml and 0.74 microgram/ml at 1 and 4 hours after administration, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Bacterial Infections↗

PubMed1992

Cytosolic Ca(2+)-induced modulation of ion selectivity and amiloride sensitivity of a cation channel and beta agonist action in fetal lung epithelium.

The cytosolic Ca2+ concentration ([Ca2+]i) affects many cell functions, including the modulation of ion channel activity. In this study patch clamp experiments using primary cultures of fetal distal lung epithelium (FDLE) demonstrated that the elevation of [Ca2+]i modulated a 25pS amiloride-blockable non selective cation (NSC) channel's ion selectivity and sensitivity to amiloride. An elevation of [Ca2+]i from 0.1 microM to 1mM both increased open probability (Po) and decreased the ratio of the permeability to Na to the permeability to K (PNa/PK) from 1.96 +/- 0.11 (SEM, n = 6) to 0.88 +/- 0.04 (n = 6). Within the range of [Ca2+]i from 0.1 microM to 100 microM amiloride (0.5 microM) decreased Po, however amiloride (0.5 microM) no longer affected Po of the NSC channel when [Ca2+]i was increased to 1mM under physiologic membrane potentials. A beta adrenergic agonist (terbutaline, 10 microM) increased Po in cell-attached patches from almost 0 (Po less than 0.01; n = 9) to 0.39 +/- 0.09 (n = 9) and [Ca2+]i from 40 +/- 6nM (n = 9) to more than 1 microM. This suggested that amiloride-blockable NSC channel activity and ion permeability are modulated by changes in [Ca2+]i near physiologic membrane potentials and a beta adrenergic agonist increases [Ca2+]i to more than 1 microM (unlike other epithelial including adult alveolar cells) which is associated with activation the NSC channel.

Amiloride↗