Local-regional anesthesia in the management of stingray stings: Experience of the Bouffard medical-surgical hospital in Djibouti.

Stingray injuries are very painful. Systemic analgesics are ineffective, and the use of local-regional anesthesia has been reported. This retrospective descriptive study reviewed all cases of stingray injuries seen at the emergency department of the Bouffard Hospital (Djbouti, Africa) between 2011 and 2014. The study included 35 patients. Most of the injuries (n= 31, 89%) concerned the lower limbs. Median pain intensity was 6 [5-8] on a visual analog scale of 0 (no pain) to 10. The following systemic medications were administered: acetaminophen to 13 (27%) patients, morphine to 8 (23%), and tramadol to 6 (17%). In all, 25 (71%) patients received local-regional anesthesia, 15 (60%) by injections at the ankle. All procedures were successful, and no adverse event was reported. This study reports clinical data about stingray injuries in the Red Sea area and highlights the interest of local-regional anesthesia in their management. Most of the procedures were distal and could be performed by trained emergency physicians.

[Tuberculous pericarditis: still a relevant disease]. / La péricardite tuberculeuse: un diagnostic qui reste d'actualité

Vaccination against tuberculosis is not an obligation anymore in France, except for children at risk, but this disease remains not so rare, including its extrapulmonary forms. The authors report the case of a 27-year-old Madagascan HIV seronegative patient, who developed a pericardial effusion when coming back from a long stay in Madagascar. An anti-inflammatory treatment and then a probabilistic antibiotic treatment were ineffective, and at the same time echocardiographic signs of tamponade appeared. As a consequence, it was decided to perform a surgical pericardial drainage and a biopsy, and to introduce an antituberculosis chemotherapy, given the epidemiologic status. The course was then quickly favorable. The presence of granulomatous inflammation on the biopsy and an elevated pericardial adenosine deaminase activity level retrospectively supported the diagnosis of tuberculous pericarditis.

An amino acid triplet in the NH2 terminus of rat ROMK1 determines interaction with SUR2B.

ATP-regulated (K(ATP)) channels are formed by an inward rectifier pore-forming subunit (Kir) and a sulfonylurea (glibenclamide)-binding protein, a member of the ATP binding cassette family (sulfonylurea receptor (SUR) or cystic fibrosis transmembrane conductance regulator). The latter is required to confer glibenclamide sensitivity to K(ATP) channels. In the mammalian kidney ROMK1-3 are components of K(ATP) channels that mediate K(+) secretion into urine. ROMK1 and ROMK3 splice variants share the core polypeptide of ROMK2 but also have distinct NH(2)-terminal extensions of 19 and 26 amino acids, respectively. The SUR2B is also expressed in rat kidney tubules and may combine with Kir.1 to form renal K(ATP) channels. Our previous studies showed that co-expression of ROMK2, but not ROMK1 or ROMK3, with rat SUR2B in oocytes generated glibenclamide-sensitive K(+) currents. These data suggest that the NH(2)-terminal extensions in both ROMK1 and ROMK3 block ROMK-SUR2B interaction. Seven amino acids in the NH(2)-terminal extensions of ROMK1 and ROMK3 are identical (amino acids 13-19 in ROMK1 and 20-26 in ROMK3) and may determine ROMK-SUR2B interaction. We constructed a series of hemagglutinin-tagged ROMK1 NH(2)-terminal deletion and substitution mutants and examined glibenclamide-sensitive K(+) currents in oocytes when co-expressed with SUR2B. These studies identified an amino acid triplet "IRA" within the conserved segment in the NH(2) terminus of ROMK1 and ROMK3 that blocks the ability of SUR2B to confer glibenclamide sensitivity to the expressed K(+) currents. The position of this triplet in the ROMK1 NH(2)-terminal extension is also important for the ROMK-SUR2B interactions. In vitro co-translation and immunoprecipitation studies with hemagglutinin-tagged ROMK mutants and SUR2B indicted that direct interaction between these two proteins is required for glibenclamide sensitivity of induced K(+) currents in oocytes. These results suggest that the IRA triplet in the NH(2)-terminal extensions of both ROMK1 and ROMK3 plays a key role in subunit assembly of the renal secretary K(ATP) channel.

From stones to bones: the biology of ClC chloride channels.

Chloride (Cl(-)) is the most abundant extracellular anion in multicellular organisms. Passive movement of Cl(-) through membrane ion channels enables several cellular and physiological processes including transepithelial salt transport, electrical excitability, cell volume regulation and acidification of internal and external compartments. One family of proteins mediating Cl(-) permeability, the ClC channels, has emerged as important for all of these biological processes. The importance of ClC channels has in part been realized through studies of inherited human diseases and genetically engineered mice that display a wide range of phenotypes from kidney stones to petrified bones. These recent findings have demonstrated many eclectic functions of ClC channels and have placed Cl(-) channels in the physiological limelight.

Cell-volume changes and ion conductances in amphibian gallbladder epithelium.

Cell-volume regulation after hyposmotic swelling is common in transporting epithelial cells. Acute regulatory volume decrease is mediated in several cell types by loss of K(+) and Cl(-) via channels either activated by the swelling phenomenon or active in the cell membrane prior to swelling. In the last two decades, it has become clear that many features of cell-volume regulation mediated by ion fluxes vary considerably among cell types. In some instances, the ion channel activation, although demonstrable, is insufficient to account, on the basis of ion fluxes, for the measured cell volume changes. Here we review the case of a salt-transporting epithelium in which hyposmotic cell swelling activates plasma membrane K(+) channels, but at the same time inhibits Cl(-) channels, thus preventing an acute volume-regulatory response. The sequence of events following cell swelling appears to be as follows: K(+) channels are activated by membrane stretch, the cell membrane hyperpolarizes (the voltage moves closer to the K(+) equilibrium potential) and this hyperpolarization reduces the Cl(-) conductance, likely by a reduction in open probability of voltage-sensitive Cl(-) channels. The significance of this phenomenon may be related to the preservation of intracellular Cl(-) rather than cell volume, or to a physiological 'need' to prevent shrinkage of cells stimulated by hormones or other mediators.

Rat homolog of sulfonylurea receptor 2B determines glibenclamide sensitivity of ROMK2 in Xenopus laevis oocyte.

Recent studies showed that coexpression of Kir6.1 or Kir6.2 with the sulfonylurea receptor (SUR1, SUR2A, or SUR2B) reconstituted an inwardly rectifying, ATP-sensitive K(+) channel that was inhibited by glibenclamide (2, 15-17). Here we report the isolation of a rat homolog of mouse SUR2B (denoted rSUR2B) from a rat kidney cDNA library. The rSUR2B sequence contains a 4,635-bp open reading frame that encodes a 1,545-amino acid polypeptide, showing 67% shared identity with SUR1 (a pancreatic beta-cell isoform) and 98% with both SUR2A (a brain isoform) and SUR2B (a vascular smooth muscle isoform). Consistent with the predicted structures of other members of the ATP-binding cassette (ABC) superfamily, the sequence of rSUR2B contains 17 putative membrane-spanning segments. Also, predicted Walker A and B consensus binding motifs, present in other ABC members, are conserved in the rSUR2B sequence. RT-PCR revealed that rSUR2B is widely expressed in various rat tissues including brain, colon, heart, kidney, liver, skeletal muscle, and spleen. The intrarenal distribution of the rSUR2B transcript was investigated using RT-PCR and Southern blot of microdissected tubules. The rSUR2B transcript was detected in proximal tubule, cortical thick ascending limb, distal collecting tubule, cortical collecting duct, and outer medullary collecting duct, but not medullary thick ascending limb. This distal distribution overlaps with that of ROMK. Coexpression of rSUR2B with ROMK2 cRNA (in 1:10 ratio) in Xenopus laevis oocytes resulted in whole cell Ba(2+)-sensitive K(+) currents that were inhibited by glibenclamide (50% inhibition with 0.2 mM glibenclamide). In contrast, rSUR2B did not confer significant glibenclamide sensitivity to oocytes coinjected with ROMK1 or ROMK3. The interaction between ROMK2 and rSUR2B was further studied by coimmunoprecipitation of in vitro translated rSUR2B and ROMK2. In agreement with the functional data, the rSUR2B protein was coimmunoprecipitated with ROMK2 in the ROMK2-rSUR2B cotranslated samples. Our data demonstrate that ROMK2, but not ROMK1 and ROMK3, can interact with rSUR2B to confer a sulfonylurea-sensitive K(+) channel, implicating SUR proteins in forming and regulating renal ATP-sensitive K(+) channels. The ROMK isoform specificity of glibenclamide effects suggests that the NH(2) terminus of the ROMK protein mediates rSUR2B-ROMK2 interactions.

Mechanism of inhibition of P-glycoprotein-mediated drug transport by protein kinase C blockers.

P-glycoprotein is a membrane ATPase that transports drugs out of cells and confers resistance to a variety of chemically unrelated drugs (multidrug resistance). P-glycoprotein is phosphorylated by protein kinase C (PKC), and PKC blockers reduce P-glycoprotein phosphorylation and increase drug accumulation. These observations suggest that phosphorylation of P-glycoprotein stimulates drug transport. However, there is evidence that PKC inhibitors directly interact with P-glycoprotein, and therefore the mechanism of their effects on P-glycoprotein-mediated drug transport and the possible role of phosphorylation in the regulation of P-glycoprotein function remain unclear. In the present work, we studied the effects of different kinds of PKC inhibitors on drug transport in cells expressing wild-type human P-glycoprotein and a PKC phosphorylation-defective mutant. We demonstrated that PKC blockers inhibit drug transport hy mechanisms independent of P-glycoprotein phosphorylation. Inhibition by the blockers occurs by (i) direct competition with transported drugs for binding to P-glycoprotein, and (ii) indirect inhibition through a pathway that involves PKC inhibition, but is independent of P-glycoprotein phosphorylation. The effects of the blockers on P-glycoprotein phosphorylation do not seem to play an important role, but the PKC-signaling pathway regulates P-glycoprotein-mediated drug transport.

Inhibition of P-glycoprotein-mediated transport by a hydrophobic contaminant in commercial gluconate salts.

The substitution of gluconate for Cl- is commonly used to characterize Cl- transport or Cl--dependent transport mechanisms. We evaluated the effects of substituting gluconate for Cl- on the transport of the P-glycoprotein substrate rhodamine 123 (R123). The replacement of Ringer solution containing Cl- (Cl--Ringer) with gluconate-Ringer inhibited R123 efflux, whereas the replacement of Cl- by other anions (sulfate or cyclamate) had no effect. The inhibition of R123 efflux by gluconate-Ringer was absent after chloroform extraction of the sodium gluconate salt. The readdition of the sodium gluconate-chloroform extract to the extracted gluconate-Ringer or to cyclamate-Ringer inhibited R123 efflux, whereas its addition to Cl--Ringer had no effect. These observations indicate that the inhibition of P-glycoprotein-mediated R123 transport by gluconate is due to one or more chloroform-soluble contaminants and that the inhibition is absent in the presence of Cl-. The results are consistent with the fact that P-glycoprotein substrates are hydrophobic. Care should be taken when replacing ions to evaluate membrane transport mechanisms because highly pure commercial preparations may still contain potent contaminants that affect transport.

Stretch-activated single K+ channels account for whole-cell currents elicited by swelling.

Functionally significant stretch-activated ion channels have been clearly identified in excitable cells. Although single-channel studies suggest their expression in other cell types, their activity in the whole-cell configuration has not been shown. This discrepancy makes their physiological significance doubtful and suggests that their mechanical activation is artifactual. Possible roles for these molecules in nonexcitable cells are acute cell-volume regulation and, in epithelial cells, the complex adjustment of ion fluxes across individual cell membranes when the rate of transepithelial transport changes. We report the results of experiments on isolated epithelial cells expressing in the basolateral membrane stretch-activated K+ channels demonstrable by the cell-attached patch-clamp technique. In these cells, reversible whole-cell currents were elicited by both isosmotic and hyposmotic cell swelling. Cation selectivity and block by inorganic agents were the same for single-channel and whole-cell currents, indicating that the same entity underlies single-channel and whole-cell currents and that the single-channel events are not artifactual. In these cells, when the rate of apical-membrane NaCl entry increases, the cell Na+ content and volume also increase, stimulating the Na+,K+-ATPase at the basolateral membrane, i.e., both Na+ extrusion and K+ uptake increase. We speculate that, under these conditions, the parallel activation of basolateral K+ channels (by the swelling) elevates conductive K+ loss, tending to maintain the cell K+ content constant ("pump-leak parallelism"). This study describes a physiologically relevant stretch-activated channel, at both the single-channel and whole-cell levels, in a nonneural cell type.

Phosphorylation of P-glycoprotein by PKA and PKC modulates swelling-activated Cl- currents.

Several proteins belonging to the ATP-binding cassette superfamily can affect ion channel function. These include the cystic fibrosis transmembrane conductance regulator, the sulfonylurea receptor, and the multidrug resistance protein P-glycoprotein (MDR1). We measured whole cell swelling-activated Cl- currents (ICl,swell) in parental cells and cells expressing wild-type MDR1 or a phosphorylation-defective mutant (Ser-661, Ser-667, and Ser-671 replaced by Ala). Stimulation of protein kinase C (PKC) with a phorbol ester reduced the rate of increase in ICl,swell only in cells that express MDR1. PKC stimulation had no effect on steady-state ICl,swell. Stimulation of protein kinase A (PKA) with 8-bromoadenosine 3',5'-cyclic monophosphate reduced steady-state ICl, swell only in MDR1-expressing cells. PKA stimulation had no effect on the rate of ICl,swell activation. The effects of stimulation of PKA and PKC on ICl,swell were additive (i.e., decrease in the rate of activation and reduction in steady-state ICl,swell). The effects of PKA and PKC stimulation were absent in cells expressing the phosphorylation-defective mutant. In summary, it is likely that phosphorylation of MDR1 by PKA and by PKC alters swelling-activated Cl- channels by independent mechanisms and that Ser-661, Ser-667, and Ser-671 are involved in the responses of ICl,swell to stimulation of PKA and PKC. These results support the notion that MDR1 phosphorylation affects ICl,swell.

Mechanical effects of pharyngeal constrictor activation on pharyngeal airway function.

The mechanical effects of pharyngeal constrictor (PC) muscle activation on pharyngeal airway function were determined in 20 decerebrate, tracheotomized cats. In 10 cats, a high-compliance balloon attached to a pressure transducer was partially inflated to just occlude the pharyngeal airway. During progressive hyperoxic hypercapnia, changes in pharyngeal balloon pressure were directly related to phasic expiratory hyopharyngeus (middle PC) activity. In two separate protocols in 10 additional cats, the following measurements were obtained with and without bilateral electrical stimulation (0.2-ms duration, threshold voltage) of the distal cut end of the vagus nerve's pharyngeal branch supplying PC motor output: 1) pressure-volume relationships in an isolated, sealed upper airway at a stimulation frequency of 30 Hz and 2) rostrally directed axial force over a stimulation frequency range of 0-40 Hz. Airway compliance determined from the pressure-volume relationships decreased with PC stimulation at and below resting airway volume. Compared with the unstimulated condition, PC stimulation increased airway pressure at airway volumes at and above resting volume. This constrictor effect progressively diminished as airway volume was brought below resting volume. At relatively low airway volumes below resting volume, PC stimulation decreased airway pressure compared with that without stimulation. PC stimulation generated a rostrally directed axial force that was directly related to stimulation frequency. The results indicate that PC activation stiffens the pharyngeal airway, exerting both radial and axial effects. The radial effects are dependent on airway volume: constriction of the airway at relatively high airway volumes, and dilation of the airway at relatively low airway volumes. The results imply that, under certain conditions, PC muscle activation may promote pharyngeal airway patency.

Isolated epithelial cells from amphibian urinary bladder express functional gap junctional hemichannels.

Exposure of the urinary bladder epithelium of Necturus maculosus (NUB) to protease and collagenase yields approximately 50% isolated polarized cells. These cells express a membrane current slowly activated by depolarization or by removal of external divalent cations. The biophysical and pharmacological properties of the current are largely consistent with those of gap junctional hemichannels. After removal of divalent cations, the cells can also be loaded with 5(6)-carboxyfluorescein, a hydrophilic fluorescent anionic dye, and exposure to dye reduces the current in a manner dependent on membrane voltage and side of application. In contrast, Necturus gallbladder (NGB) cells exhibit no membrane conductance attributable to gap junctional hemichannels, although previous studies reveal the persistence of gap junction plaques on the plasma membrane. We conclude that functional gap junctional hemichannels can be expressed on the surface of certain isolated epithelial cells and that this is not a necessary consequence of the isolation procedure. These structures may contribute to cell damage under pathological conditions involving cell detachment.

Swelling-activated chloride currents in a drug-sensitive cell line and a P glycoprotein-expressing derivative are underlied by channels with the same pharmacological properties.

It has been proposed that P glycoprotein (Pgp) expression is associated with swelling-activated Cl- currents in multidrug-resistant cells. The Pgp substrate vinblastine and the modulator verapamil produced a reversible concentration-dependent block of swelling-activated Cl- currents in both a drug-sensitive cell line (MCF-7) and a Pgp-expressing derivative (BC19/3). The similarity of the results obtained in both cell lines suggests that the mechanism of block is not related to Pgp expression and supports the hypothesis that Pgp expression is not necessary for the swelling activation of Cl- currents. In contrast to the results obtained with vinblastine, two other cytoskeleton-disrupting agents, colchicine and cytochalasin D, were not able to affect the swelling-activated Cl- currents in either cell line. The data provided no evidence for the involvement of the cytoskeleton in the swelling activation of Cl- channels in these cell lines. The Cl- channel blockers, 5-nitro-2-(3-phenylpropylamino)benzoic acid and 4, 4'-diisothiocyanatostilbene-2,2'-disulfonic acid, each produced a similar reversible concentration-dependent block in the swelling-activated currents in both the Pgp-expressing and nonexpressing cells. This strongly suggests that the Cl- channel(s) responsible for the swelling-dependent current in both cell lines are the same and, since MCF-7 cells do not express Pgp, that Pgp is not the channel responsible for the volume-activated Cl- currents in these cells.

P-glycoprotein is not a swelling-activated Cl- channel; possible role as a Cl- channel regulator.

1. The whole-cell configuration of the patch-clamp technique was used to determine if P-glycoprotein (Pgp) is a swelling-activated Cl- channel. 2. Hamster pgp1 cDNA was transfected into a mouse fibroblast cell line resulting in expression of functional Pgp in the plasma membrane. This cell line was obtained without exposure to chemotherapeutic agents. 3. Swelling-activated whole-cell Cl- current (ICl,swell) was elicited by lowering the bath osmolality. ICl,swell was characterized in detail in the pgp1-transfected mouse cell line and compared with that of its parental cell line. Expression of Pgp did not modify the magnitude or properties of ICl,swell, except that addition of the anti-Pgp antibody C219 to the pipette solution inhibited this current by 75% only in the Pgp-expressing cells. 4. ICl,swell in the mouse Pgp-expressing cell line was compared with that in a Pgp-expressing hamster fibroblast cell line. The characteristics of ICl,swell (voltage dependence, blocker sensitivity, anion selectivity sequence, requirement for hydrolysable ATP) in Pgp-expressing cells were different between the two cell lines. These results suggest that the channel(s) responsible for ICl,swell are different between the two cell lines. In addition, C219 inhibited ICl,swell in both Pgp-expressing cell lines, even though they seem to express different swelling-activated Cl- channels. 5. We conclude that firstly, Pgp is not a swelling-activated Cl- channel; secondly, it possibly functions as a Cl- channel regulator; and thirdly, ICl,swell is underlined by different Cl- channels in different cells.

Respiratory-related pharyngeal constrictor muscle activity in normal human adults.

Electromyographic activity of the superior, middle, and inferior pharyngeal constrictor (PC) muscles was examined in 10 normal adult humans during wakefulness and sleep. Wire electrodes were inserted close to the midline of the posterior pharyngeal wall at the level of the soft palate (superior PC), tip of the epiglottis (middle PC), and corniculate tubercle (inferior PC). In general, the three PC muscles exhibited similar patterns of activation. The PCs were activated during swallows, repetitive "pa" sounds, changes in head position, and the last portions of slow inspiratory and expiratory vital capacity maneuvers. Respiratory-related PC activity was infrequent during quiet breathing during wakefulness; variable and inconsistent phasic activation in expiration in one or more of the PCs was present in seven of the 10 subjects, particularly after a swallow. Progressive hyperoxic hypercapnia and progressive isocapnic hypoxia were associated with recruitment of phasic PC activity, which was predominantly expiratory; however, variable discharge patterns were observed within a given muscle and a given subject. When phasic PC activity was present, preactivation during late inspiration was frequently observed. PC activity was absent in NREM sleep and exhibited sporadic, nonrespiratory-related bursts of activity during REM sleep. Passively induced hypocapnic hyperventilation in NREM sleep was not associated with PC activation. The results indicate that the PCs have very similar patterns of activation and exhibit phasic expiratory activity during relatively high ventilatory output states in wakefulness.

Differential activity of the pars recta and pars oblique in fundamental frequency control.

This study was designed to determine if differences exist in pars recta and pars oblique muscle activity during speech and singing. Hooked wire electrodes were implanted in the muscle bundles under direct vision during thyroid surgery in two men and three women. It was found that the pars recta and pars oblique do not function in a similar manner across fundamental frequencies (fo's), tasks, or subjects. Large inter- and intrasubject variability was evident in the contribution of the cricothyroid bundles to fundamental frequency (fo) control. It is speculated that the effect of pars recta and pars oblique contraction may be a function of individual anatomic variations.

Activation of intrinsic laryngeal muscles during cough.

We studied the pattern of discharge of the posterior cricoarytenoid (PCA), cricothyroid (CT), thyroarytenoid (TA), and arytenoideus transversus (AR) muscles during cough in 12 anesthetized dogs. Diaphragm electromyographic (EMG) activity was also recorded, together with subglottic and esophageal pressures. Trains of repetitive coughs were induced by mechanically stimulating the tracheobronchial airway. Trials with the upper airway isolated from and connected to the lower airway were performed before and following bilateral sectioning of the internal branch of the superior laryngeal nerve (SLN). The immediate effect of tracheal stimulation was an "apneic" period at FRC, during which the PCA, a laryngeal abductor, showed a progressive increase in activity accompanied by small, variable increases in the activity of the CT and the laryngeal adductors, the TA and AR. The subsequent cough efforts were divided into three phases: inspiration, glottic narrowing, and forced expiration. PCA activity was greatest during the inspiratory phase and CT activity was greatest during the expiratory phase. Peak subglottic pressure occurred during glottic narrowing and coincided with the greatest activation of the TA and AR during the cough effort, and suppression of the PCA and CT. The patterns of EMG activation were not affected by the route of breathing or SLN section. The results suggest the presence of a uniquely central process controlling laryngeal muscles during cough, independent of laryngeal sensory feedback.

Respiratory-related pharyngeal constrictor muscle activity in decerebrate cats.

Respiratory-related activity of the hyopharyngeus (middle pharyngeal constrictor) and thyropharyngeus (inferior pharyngeal constrictor) muscles was determined in decerebrate, tracheotomized adult cats and compared with the electromyographic activity of the thyroarytenoid, a vocal cord adductor. During quiet breathing, the hyopharyngeus and usually the thyroarytenoid exhibited phasic activity during expiration and tonic activity throughout the respiratory cycle. Respiratory-related thyropharyngeus activity was absent under these conditions. Progressive hyperoxic hypercapnia and progressive isocapnic hypoxia increased phasic expiratory activity in both pharyngeal constrictor (PC) muscles but tended to suppress thyroarytenoid activity. Passively induced hypocapnia and the central apnea that followed the cessation of the mechanical hyperventilation were associated with tonic activation of the hyopharyngeus and thyroarytenoid but no recruitment in thyropharyngeus activity. The expiratory phase of a sigh and progressive pneumothorax were associated with an increase in phasic thyroarytenoid activity but no change in phasic PC activity. The results indicate that a variety of stimuli modulate respiratory-related PC activity, suggesting that the PC muscles may have a role in the regulation of upper airway patency during respiration.

Comparison of direct and indirect calculations of laryngeal airway resistance in connected speech.

Direct measures of subglottal pressure obtained through a tracheal puncture were used to calculate laryngeal airway resistance. Six subjects completed tasks including syllable trains and more natural speech samples produced at three loudness levels. Direct calculations of natural speech resistance values were compared with indirect estimates obtained during syllable train production. The degree of correspondence between direct and indirect calculations varied by subject. Overall, the smallest relative errors among calculations occurred for syllable trains, with higher relative errors for the monologue and sentence. For loudness conditions, the smallest and largest relative errors occurred for soft and loud productions, respectively. The clinical utility of indirect estimation is questioned and suggestions for improving its validity are provided.

P-glycoprotein-associated chloride currents revealed by specific block by an anti-P-glycoprotein antibody.

The relationships between P-glycoprotein (PGP) expression and plasma membrane ion currents activated by cell swelling were studied in several cell lines by use of the whole cell configuration of the patch-clamp technique. Swelling-activated Cl- currents (ICls) had similar characteristics independently of whether PGP was expressed. Addition of the anti-PGP monoclonal antibody C219 or its Fab fragment to the pipette solution prevented ICls in cells expressing functional PGP (assessed by immunoblots, immunofluorescence, and transport of rhodamine 123) but not in cells lacking PGP expression. A peptide analogue of the C219 epitope abolished the effect of C219. Other anti-PGP antibodies and mouse immunoglobulin G were ineffective. C219 did not alter swelling-activated cation currents. Inasmuch as ICls is present in cells that do not express PGP and C219 has no effect on ICls in these cells, we conclude that PGP is not required for the ICls phenotype. However, when expressed in the plasma membrane, PGP is involved, directly or indirectly, in ICls but not in swelling-activated K+ currents.