Early Versus Delayed Autologous Stem Cell Transplantation and Interferon Maintenance in Multiple Myeloma: Single-Center Experience of 18 Years.

BACKGROUND: Autologous stem cell transplantation (ASCT) has become the mainstay of 1st-line treatment in younger patients with multiple myeloma (MM), but statistical confirmation of its superiority over other therapies, especially in the era of novel agents, is still lacking. METHODS: We reviewed the results of all 548 myeloma ASCTs performed in our institute over the past 18 years. RESULTS: More than one-half of the patients had access to novel agents before their transplantations. Although the age of the transplanted patients increased significantly over the years, treatment-related mortality (TRM) was remarkably low, especially in 1st-line transplanted patients (100-day TRM, 0.3%). The median overall survival (OS) of the entire cohort was 98.4 months. Patients transplanted within 12 months from the start of their therapy had significantly better responses than those having delayed ASCT (complete response rate, 58.1% vs 46.8%; P = .016) and significant post-ASCT progression-free survival (PFS) benefit (30.2 [26.1-34.3] mo vs 23.3 [16.8-29.8] mo; P = .036), but we found no significant overall survival difference. The results were similar in patients treated with or without novel agents before ASCT. During a period of time, interferon maintenance was our standard approach to post-ASCT maintenance. Our analysis showed not only a significant PFS advantage with interferon, but also a highly significant overall survival benefit (150.4 [105.1-195.8] mo vs 86.1 [72.5-99.7] mo; P = .003). CONCLUSIONS: Our findings demonstrate that delayed ASCT can be feasible in selected patients.

Autologous haematopoietic stem cell mobilisation in multiple myeloma and lymphoma patients: a position statement from the European Group for Blood and Marrow Transplantation.

Autologous haematopoietic SCT with PBSCs is regularly used to restore BM function in patients with multiple myeloma or lymphoma after myeloablative chemotherapy. Twenty-eight experts from the European Group for Blood and Marrow Transplantation developed a position statement on the best approaches to mobilising PBSCs and on possibilities of optimising graft yields in patients who mobilise poorly. Choosing the appropriate mobilisation regimen, based on patients' disease stage and condition, and optimising the apheresis protocol can improve mobilisation outcomes. Several factors may influence mobilisation outcomes, including older age, a more advanced disease stage, the type of prior chemotherapy (e.g., fludarabine or melphalan), prior irradiation or a higher number of prior treatment lines. The most robust predictive factor for poor PBSC collection is the CD34(+) cell count in PB before apheresis. Determination of the CD34(+) cell count in PB before apheresis helps to identify patients at risk of poor PBSC collection and allows pre-emptive intervention to rescue mobilisation in these patients. Such a proactive approach might help to overcome deficiencies in stem cell mobilisation and offers a rationale for the use of novel mobilisation agents.

Successful treatment of renal failure caused by multiple myeloma with HLA-identical living kidney and bone marrow transplantation: a case report.

Here we have described a successful HLA-identical living allogeneic kidney transplantation after bone marrow transplantation in a patient with end-stag liver disease caused by multiple myeloma (MM). Our case is unique, because this combined transplantation is rarely possible and because of our unique immunosuppressive and management strategies. A 45-year-old man with ESRD MM and κ light-chain nephropathy was diagnosed. Cytostatic treatment resulted in partial remission, so autologous peripheral stem cell transplantation (SCT) was performed leading to a complete remission; however the patient remained anuric. The patient's HLA-identical brother offered to be a donor of peripheral stem cells for collection and cryopreservation. Kidney transplantation was performed with a combination of tacrolimus sirolimuns, and methylprednisolone. With a well-functioning kidney graft, allogeneic SCT was performed in the incipient relapse phase of MM, after total body irradiation. Severe oropharyngeal infections, diarrhea, sepsis, and renal failure. Fearing acute renal rejection, we administered steroid bolus. He experienced therapy with gradual restoration of kidney function. Then, steroid-responsive acute graft-versus-host disease (grade II, predominantly bowel) was diagnosed on the background of diarrhea, which returned once. Later he experienced a left subclavian vein thrombosis at the site of a central venous catheter and sepsis. Having recovered from these events, the patient enjoys good health, with stable kidney function and normal protein excretion. After the steroid was stopped, a bone marrow biopsy revealed full-donor type normocellular hemopoiesis. Because of the chimerism, we gradually discontinued the immunosuppression including, sirolimus and finally tacrolimus, since with minimal trough levels there were no complications. Bone marrow biopsy showed a complete remission. In MM with ESRD HLA-identical combined kidney and bone marrow transplantation from a living donor may offer not only complete remission and good renal function, but also good health without immunosuppression.

European data on stem cell mobilization with plerixafor in non-Hodgkin's lymphoma, Hodgkin's lymphoma and multiple myeloma patients. A subgroup analysis of the European Consortium of stem cell mobilization.

The effectiveness of the novel hematopoietic stem cell mobilizing agent plerixafor was evaluated in nationwide compassionate use programs in 13 European countries. A total of 580 poor mobilizers with non-Hodgkin's lymphoma (NHL), Hodgkin's lymphoma (HL) and multiple myeloma (MM) were enrolled. All patients received plerixafor plus granulocyte CSF with or without chemotherapy. Overall, the collection yield was significantly higher in MM patients (>2.0 × 10(6) CD34+ cells/kg: 81.6%; >5.0 × 10(6) CD34+ cells/kg: 32.0%) than in NHL patients (>2.0 × 10(6) CD34+ cells/kg: 64.8%; >5.0 × 10(6) CD34+ cells/kg: 12.6%; P<0.0001) and also significantly higher in HL patients (>2.0 × 10(6) CD34+ cells/kg: 81.5%; >5.0 × 10(6) CD34+ cells/kg: 22.2%) than in NHL patients (P=0.013). In a subgroup analysis, there were no significant differences in mobilization success comparing patients with diffuse large B-cell lymphoma, follicular lymphoma and mantle cell lymphoma. Our data emphasize the role of plerixafor in poor mobilizers, but further strategies to improve the apheresis yield especially in patients with NHL are required.

Plerixafor for PBSC mobilisation in myeloma patients with advanced renal failure: safety and efficacy data in a series of 21 patients from Europe and the USA.

We describe 20 patients with myeloma and 1 with primary amyloidosis from 15 centres, all with advanced renal failure, most of whom had PBSC mobilised using plerixafor following previous failed mobilisation by conventional means (plerixafor used up-front for 4 patients). For 15 patients, the plerixafor dose was reduced to 0.16 mg/kg/day, with a subsequent dose increase in one case to 0.24 mg/kg/day. The remaining six patients received a standard plerixafor dosage at 0.24 mg/kg/day. Scheduling of plerixafor and apheresis around dialysis was generally straightforward. Following plerixafor administration, all patients underwent apheresis. A median CD34+ cell dose of 4.6 × 10(6) per kg was achieved after 1 (n=7), 2 (n=10), 3 (n=3) or 4 (n=1) aphereses. Only one patient failed to achieve a sufficient cell dose for transplant: she subsequently underwent delayed re-mobilisation using G-CSF with plerixafor 0.24 mg/kg/day, resulting in a CD34+ cell dose of 2.12 × 10(6)/kg. Sixteen patients experienced no plerixafor toxicities; five had mild-to-moderate gastrointestinal symptoms that did not prevent apheresis. Fifteen patients have progressed to autologous transplant, of whom 12 remain alive without disease progression. Two patients recovered endogenous renal function post autograft, and a third underwent successful renal transplantation. Plerixafor is highly effective in mobilising PBSC in this difficult patient group.

Endotoxins do not influence transplacental transmission of lymphotropic human herpesviruses and human papillomaviruses into amniotic fluid taken from healthy mothers before parturition in Hungary.

Pregnant women were examined following healthy pregnancies at term. Amniotic fluids were sampled before arteficial rupture of membranes using closed vacutainer system. Blood samples were also taken from the pregnants simultaneously. Endotoxin concentrations of amniotic fluids were tested by the semiquantitative Limulus amebocyte lysate. Both amniotic fluids and blood samples were tested for the presence of DNA of lymphotropic human herpesviruses. The DNA of human papillomaviruses were tested only in the amniotic fluid samples. One-third of the amniotic fluids tested were found to contain measurable amounts of endotoxin. Lymphotropic herpesvirus DNA was deteced in every fourth amniotic fluid sample and in every 8th blood sample. The prevalence of papillomaviruses was 7 of 96 samples. No significant correlation was found between the presence of endotoxin and viruses in the amniotic fluids. Epstein-Barr virus, human cytomegalovirus and human herpesvirus type 7 were found more frequently in the amniotic fluids than in blood samples (7 to 1). The prevalence of human herpesvirus 6 and 8 was higher in the blood samples than that in the amniotic fluids. The mean weight of the neonates were not impaired significantly by the presence of either viruses or endotoxin. Possible post partum consequences, i.e. partial immunotolerance to viruses is discussed.

[Role of thalidomide in the treatment of multiple myeloma]. / A thalidomid szerepe a myeloma multiplex gyógykezelésében.

Multiple myeloma is a relatively common hematologic malignancy with no definitive treatment available. Although, therapy may include allogenic bone marrow transplantation, high-dose ablative chemotherapy followed by bone marrow or peripheral stem cell transplantation, melphalan/corticosteroid therapy, alpha-interferon treatment, and combined cytostatic chemotherapy, currently none of these alternatives offers cure for the disease. Thalidomide is an infamous molecule for its teratogenicity, yet it possesses potent immunomodulatory, anti-angiogeneic and, in higher concentrations, direct anti-myeloma-cell properties. At present, the drug is only approved for the treatment of erythema nodosum of leprosy, however, there are several preliminary results that show clinical efficacy in multiple myeloma. This drug has especially potent anti-myeloma effects in combinations with dexamethasone and certain cytostatic chemotherapeutic agents. The effects are evident both in polyresistant, and relapsing myeloma, a form with no accepted effective treatment options. In this paper, the fundamental molecular and cellular effects of thalidomide are summarized then the most important clinical studies with thalidomide are reviewed. It is the authors' hope that thalidomide will soon be a full member of the medical arsenal in the fight against multiple myeloma.

Parathyroid cells express dihydropyridine-sensitive cation currents and L-type calcium channel subunits.

Parathyroid cells express Ca2+ -conducting currents that are activated by raising the extracellular Ca2+ concentration ([Ca2+]o). We investigated the sensitivity of these currents to dihydropyridines, the expression of voltage-dependent Ca(2+) channel (VDCC) subunits, and the effects of dihydropyridines on the intracellular free [Ca2+] ([Ca2+]i) and secretion in these cells. Dihydropyridine channel antagonists dose dependently suppressed Ca2+ -conducting currents, and agonists partially reversed the inhibitory effects of the antagonists in these cells. From a bovine parathyroid cDNA library, we isolated cDNA fragments encoding parts of an alpha(1S)- and a beta(3)-subunit of L-type Ca(2+) channels. The alpha(1S)-subunit cDNA from the parathyroid represents an alternatively spliced variant lacking exon 29 of the corresponding gene. Northern blot analysis and immunocytochemistry confirmed the presence of transcripts and proteins for alpha(1)- and beta(3)-subunits in the parathyroid gland. The addition of dihydropyridines had no significant effects on high [Ca2+]o-induced changes in [Ca2+]i and parathyroid hormone (PTH) release. Thus our studies indicate that parathyroid cells express alternatively spliced L-type Ca2+ channel subunits, which do not modulate acute intracellular Ca2+ responses or changes in PTH release.

Cloning of the beta(2a) subunit of the voltage-dependent calcium channel from human heart: cooperative effect of alpha(2)/delta and beta(2a) on the membrane expression of the alpha(1C) subunit.

Expression and membrane localization of an epitope-tagged human Ca(2+) channel alpha(1C) subunit were monitored in Xenopus oocytes by confocal microscopy and electrophysiological recording. When alpha(2)/delta and beta(2a) were separately coexpressed with the alpha(1C) subunit, assessment by confocal microscopy showed an 86 and 225% increase of the channel density, respectively. Simultaneous coexpression of alpha(2)/delta and beta(2a) subunits resulted in a cooperative (470%) increase. Electrophysiological measurements performed in parallel revealed that the current augmentation by the alpha(2)/delta subunit is totally attributable to an increase in channel density, whereas the beta(2a) subunit, in addition to increasing channel density, also facilitates channel opening.

Cardiac-specific overexpression of the alpha(1) subunit of the L-type voltage-dependent Ca(2+) channel in transgenic mice. Loss of isoproterenol-induced contraction.

The L-type voltage-dependent calcium channel (L-VDCC) regulates calcium influx in cardiac myocytes. Activation of the beta-adrenergic receptor (betaAR) pathway causes phosphorylation of the L-VDCC and that in turn increases Ca(2+) influx. Targeted expression of the L-VDCC alpha(1) subunit in transgenic (Tg) mouse ventricles resulted in marked blunting of the betaAR pathway. Inotropic and lusitropic responses to isoproterenol and forskolin in Tg hearts were significantly reduced. Likewise, Ca(2+) current augmentation induced by iso- proterenol and forskolin was markedly depressed in Tg cardiomyocytes. Despite no change in betaAR number, isoproterenol-stimulated adenylyl cyclase activity was absent in Tg membranes and NaF and forskolin responses were reduced. We postulate an important pathway for regulation of the betaAR by Ca(2+) channels.

Auxiliary subunits operate as a molecular switch in determining gating behaviour of the unitary N-type Ca2+ channel current in Xenopus oocytes.

1. We systematically examined the biophysical properties of omega-conotoxin GVIA-sensitive neuronal N-type channels composed of various combinations of the alpha1B, alpha2/delta and beta1b subunits in Xenopus oocytes. 2. Whole-cell recordings demonstrated that coexpression of the beta1b subunit decelerated inactivation, whereas the alpha2/delta accelerated both activation and inactivation, and cancelled the kinetic effects of the beta1b. The alpha2/delta and the beta1b controlled voltage dependence of activation differently: the beta1b significantly shifted the current-voltage relationship towards the hyperpolarizing direction; however, the alpha2/delta shifted the relationship only slightly in the depolarizing direction. The extent of voltage-dependent inactivation was modified solely by the beta1b. 3. Unitary currents measured using a cell-attached patch showed stable patterns of opening that were markedly different among subunit combinations in their kinetic parameters. The alpha2/delta and the beta1b subunits also acted antagonistically in regulating gating patterns of unitary N-type channels. Open time was shortened by the alpha2/delta, while the fraction of long opening was enhanced by the beta1b. The alpha2/delta decreased opening probability (Po), while the beta1b increased Po. alpha1Balpha2/deltabeta1b produced unitary activity with an open time distribution value in between those of alpha1Balpha2/delta and alpha1Bbeta1b. However, both the alpha2/delta and the beta1b subunits reduced the number of null traces. 4. These results suggest that the auxiliary subunits alone and in combination contribute differently in forming gating apparatuses in the N-type channel, raising the possibility that subunit interaction contributes to the generation of functional diversity of N-type channels in native neuronal preparations also.

Human herpesvirus 8 in hematologic diseases.

Human herpesvirus type 8 (HHV-8), also known as Kaposi's sarcoma-associated herpesvirus (KSHV) is a new member of the g-herpesvirus family. It is an unusual herpesvirus in that it carries a large number of genes that encode oncoproteins or cell signaling proteins. In addition to being the causative agent of both HIV-associated and non-HIV-associated Kaposi's sarcoma this DNA tumor virus has been implicated in the pathogenesis of several diseases. These include multiple myeloma (MM), Waldenstöm's macroglobulinemia (WM), multicentric Castleman's disease (MCD), body cavity-based lymphoma (BCBL), and various other conditions such as sarcoidosis and pemphigus. While the causative role of the viral infection is fairly certain in the development of BCBL and multicentric Castleman's disease, HHV-8 may act through a different mechanism to induce plasma cell malignancies. It has been suggested though the finding is still controversial - that infection of bone marrow stromal dendritic cells by HHV-8 might be a key factor in the etiology and pathogenesis of monoclonal gammopathies. The aim of this review is to provide a short introduction into the tumorigenic potential of HHV-8 as well as to detail the available data and possible mechanisms on the involvement of this virus in different hematologic diseases.

cAMP-dependent phosphorylation sites and macroscopic activity of recombinant cardiac L-type calcium channels.

The involvement of cAMP-dependent phosphorylation sites in establishing the basal activity of cardiac L-type Ca2+ channels was studied in HEK 293 cells transiently cotransfected with mutants of the human cardiac alpha1 and accessory subunits. Systematic individual or combined elimination of high consensus protein kinase A (PKA) sites, by serine to alanine substitutions at the amino and carboxyl termini of the alpha1 subunit, resulted in Ca2+ channel currents indistinguishable from those of wild type channels. Dihydropyridine (DHP)-binding characteristics were also unaltered. To explore the possible involvement of nonconsensus sites, deletion mutants were used. Carboxyl-terminal truncations of the alpha1 subunit distal to residue 1597 resulted in increased channel expression and current amplitudes. Modulation of PKA activity in cells transfected with the wild type channel or any of the mutants did not alter Ca2+ channel functions suggesting that cardiac Ca2+ channels expressed in these cells behave, in terms of lack of PKA control, like Ca2+ channels of smooth muscle cells.

Effects of 2,3-butanedione monoxime (BDM) on calcium channels expressed in Xenopus oocytes.

1. We examine the actions of a chemical phosphatase, 2,3-butanedione monoxime (BDM), on endogenous and expressed Ca2+ channel currents in Xenopus oocytes. In previous studies on L-type Ca2+ channel currents in cardiomyocytes and dorsal root ganglia, the inhibitory effects of BDM were attenuated by activation of protein kinase A. 2. Ba2+ currents (IBa) through a human wild-type L-type Ca2+ channel complex (i.e. halpha1C, alpha2-deltaa and hbeta1b) are inhibited by BDM with an IC50 of 16 mM, with 10 mM producing a 36.1 +/- 2.2 % inhibition. IBa through endogenous oocyte N-type Ca2+ channels, upregulated by exogenous alpha2-deltaa and hbeta1b subunits, are inhibited to a similar degree by BDM. 3. To examine whether the action of BDM is dependent on PKA-dependent phosphorylation, a clone of halpha1C deficient in all five serine PKA consensus sites (halpha1C-SA5) was co-expressed with alpha2-deltaa and the human cardiac hbeta3 subunit, which naturally lacks PKA consensus sites. This complex exhibited a sensitivity to BDM that was similar to the wild-type complex, with 10 mM BDM producing 31.6 +/- 1.5 % inhibition. 4. As limited proteolysis upregulates Ca2+ channels in cardiomyocytes and renders them less sensitive to BDM, experiments were performed with a carboxyl terminus deletion mutant, halpha1C-Delta1633. IBa through this subunit showed a sensitivity to BDM that was similar to the wild-type complex, with 10 mM BDM producing 31.3 +/- 1.4 % inhibition. However, co-expression with alpha2-deltaa and hbeta3 subunits reduced potency, and is reflected by an increased IC50 of 22.7 mM. 5. The actions of BDM were examined on a rat brain rbA-1 Ca2+ channel clone, alpha1A, co-expressed with alpha2-deltab and beta1b subunit homologues from rat brain. BDM inhibited the current through this channel complex to a similar degree to that seen for cardiac wild-type channels, with 10 mM BDM causing a 33.1 +/- 3.5 % inhibition. 6. The effects of BDM were compared at two holding potentials, -80 and -30 mV, using the halpha1C-Delta1633, alpha2-deltaa and hbeta3 subunit combination. At -30 mV BDM is more potent with 10 mM BDM reducing IBa by 39.8 +/- 2.7 %, compared with 20.8 +/- 2.2 % at -80 mV. 7. The data suggest that BDM may not exert its inhibitory action by means of a chemical phosphatase effect, but by channel block. The similar potency observed between alpha1C, alpha1A and endogenous (N-type) channels may help point towards a possible site of action; differences with the carboxyl deletion mutant may help further to define a locus of interaction.

Effects of temperature on human L-type cardiac Ca2+ channels expressed in Xenopus oocytes.

Temperature normally affects peak L-type Ca2+ channel (CaCh) current with a temperature coefficient (Q10) of between 1.8 and 3.5; in cardiomyocytes attenuating protein kinase A activity increases Q10 whilst activating it lowers Q10. We examine temperature effects using cloned human cardiac CaChs expressed in Xenopus oocytes. Peak inward currents (IBa) through expressed CaChs (i.e. alpha1C alpha2/deltaa beta1b) exhibited a Q10 of 5.8+/-0.4 when examined between 15 and 25 degreesC. The nifedipine-sensitive IBa exhibited a higher Q10 of 8.7+/-0.5, whilst the nifedipine-insensitive IBa exhibited Q10 of 3.7+/-0.3. Current/voltage (I/V) relationships shifted to negative potentials on warming. Using instead a different CaCh beta subunit isoform, beta2c, gave rise to an IBa similar to those expressed using beta1b. We utilized a carboxyl deletion mutant, alpha1C-Delta1633, to determine the temperature sensitivity of the pore moiety in the absence of auxiliary subunits; IBa through this channel exhibited a Q10 of 9.3+/-0.3. However, the Q10 for macroscopic conductance was reduced compared to that of heteromeric channels; decreasing from 5.0 (i.e. alpha1C alpha2/deltaa beta1b) and 3.9 (i.e. alpha1C alpha2/deltaa beta2c) to 2.4 (alpha1C-Delta1633). These observations differ markedly from those made in studies of cardiomyocytes, and suggest that enhanced sensitivity may depend on the membrane environment, channel assembly or other regulatory factors.

Inhibition of recombinant human cardiac L-type Ca2+ channel alpha1C subunits by 3-isobutyl-1-methylxanthine.

Inhibition of ion channels by the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine (IBMX) and related compounds has been demonstrated in various cell types, including the neuromuscular junction, GH3 cells and vascular smooth muscle cells. These effects may be unrelated to the actions of these compounds on cellular metabolism, intracellular Ca2+ stores and phosphodiesterase inhibition. In this study, the inhibition of recombinant human cardiac L-type Ca2+ channel alpha1C subunits by IBMX was examined using the whole-cell configuration of the patch clamp technique. Inhibition was repeatable, voltage-independent and associated with increased apparent channel inactivation. The actions of IBMX were unaffected in the presence of inhibitors of protein kinases A and G. The non-xanthine phosphodiesterase inhibitor rolipram had a small inhibitory effect on currents, but this was also unaffected by a protein kinase A inhibitor. These effects of IBMX could not be attributed to release of Ca2+ from intracellular stores. Our findings indicate that methylxanthines can inhibit the cardiac L-type Ca2+ channel alpha1C subunit in the absence of auxiliary subunits by an undetermined, possibly direct mechanism.

Hypoxia inhibits the recombinant alpha 1C subunit of the human cardiac L-type Ca2+ channel.

1. Whole-cell patch clamp recordings were used to investigate the effects of hypoxia on recombinant human L-type Ca2+ channel alpha 1C subunits stably expressed in human embryonic kidney (HEK 293) cells. 2. Ca2+ channel currents were reversibly inhibited by hypoxia (PO2 < 90 mmHg). The degree of inhibition depended on the charge carrier used, Ca2+ currents being more O2 sensitive than Ba2+ currents. 3. Hypoxic inhibition of Ca2+ channel currents was more pronounced at lower activating membrane potentials (< or = +30 mV), and was associated with a slowing of activation kinetics. Current inactivation and deactivation were unaffected by hypoxia. 4. Since hypoxia similarly regulates native L-type Ca2+ channels in vascular smooth muscle cells, our results suggest that hypoxic regulation of L-type Ca2+ channels arises from modification of structural features of the alpha 1 subunit common to cardiac and smooth muscle L-type channels.

Properties of three COOH-terminal splice variants of a human cardiac L-type Ca2+-channel alpha1-subunit.

There is growing evidence for diversity of cardiac-type (class C) voltage-dependent calcium-channel alpha1-subunits arising from the alternative splicing of a primary transcript. In this study, we show the existence of carboxy-terminal variability in the human cardiac alpha1-gene by genomic cloning. We found that the genomic DNA segment encoding the COOH-terminal tail of the protein is composed of nine invariable and two alternative exons. The alternative utilization of these latter two exons gives rise to the formation of three message variants for this region. Reverse transcription followed by polymerase chain reaction and radioanalytic quantitation of the reverse transcription-polymerase chain reaction products showed significant variations in the distribution of these isoforms (hHt alpha1, rHt alpha1, fHt alpha1) in distinct parts of the heart, the aorta, and fibroblasts. Expression of the three alpha1-isoforms in Xenopus oocytes or in HEK-293 cells and analysis of the kinetics and voltage dependence of the induced calcium-channel currents revealed only insignificant differences in the behavior of these isoforms. When the alpha1-isoforms were coexpressed with a human beta-subunit, no alpha1-specific divergences were observed, but the effects of beta-subunit coexpression on alpha1-isoform biophysical properties were confirmed. The differential abundance of the three isoforms and the influence of an accessory subunit are of potential physiological significance.