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Acevedo LM, Vidal Á, Aguilera-Tejero E, Rivero JLL. Muscle plasticity is influenced by renal function and caloric intake through the FGF23-vitamin D axis. Am J Physiol Cell Physiol 2023; 324:C14-C28. [PMID: 36409180 DOI: 10.1152/ajpcell.00306.2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Skeletal muscle, the main metabolic engine in the body of vertebrates, is endowed with great plasticity. The association between skeletal muscle plasticity and two highly prevalent health problems: renal dysfunction and obesity, which share etiologic links as well as many comorbidities, is a subject of great relevance. It is important to know how these alterations impact on the structure and function of skeletal muscle because the changes in muscle phenotype have a major influence on the quality of life of the patients. This literature review aims to discuss the influence of a nontraditional axis involving kidney, bone, and muscle on skeletal muscle plasticity. In this axis, the kidneys play a role as the main site for vitamin D activation. Renal disease leads to a direct decrease in 1,25(OH)2-vitamin D, secondary to reduction in renal functional mass, and has an indirect effect, through phosphate retention, that contributes to stimulate fibroblast growth factor 23 (FGF23) secretion by bone cells. FGF23 downregulates the renal synthesis of 1,25(OH)2-vitamin D and upregulates its metabolism. Skeletal production of FGF23 is also regulated by caloric intake: it is increased in obesity and decreased by caloric restriction, and these changes impact on 1,25(OH)2-vitamin D concentrations, which are decreased in obesity and increased after caloric restriction. Thus, both phosphate retention, that develops secondary to renal failure, and caloric intake influence 1,25(OH)2-vitamin D that in turn plays a key role in muscle anabolism.
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Affiliation(s)
- Luz M Acevedo
- Department of Comparative Anatomy and Pathological Anatomy and Toxicology, Faculty of Veterinary Sciences, Laboratory of Muscular Biopathology, University of Cordoba, Spain.,Departamento de Ciencias Biomédicas, Facultad de Ciencias Veterinarias, Universidad Central de Venezuela, Maracay, Venezuela
| | - Ángela Vidal
- Maimonides Biomedical Research Institute of Cordoba (IMIBIC), Reina Sofia University Hospital, University of Cordoba, Spain
| | - Escolástico Aguilera-Tejero
- Maimonides Biomedical Research Institute of Cordoba (IMIBIC), Reina Sofia University Hospital, University of Cordoba, Spain
| | - José-Luis L Rivero
- Department of Comparative Anatomy and Pathological Anatomy and Toxicology, Faculty of Veterinary Sciences, Laboratory of Muscular Biopathology, University of Cordoba, Spain
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Neuromuscular Manifestations of Acquired Metabolic, Endocrine, and Nutritional Disorders. Neuromuscul Disord 2022. [DOI: 10.1016/b978-0-323-71317-7.00021-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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The role of potassium in muscle membrane dysfunction in end-stage renal disease. Clin Neurophysiol 2021; 132:3125-3135. [PMID: 34740043 DOI: 10.1016/j.clinph.2021.09.012] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2021] [Revised: 08/15/2021] [Accepted: 09/01/2021] [Indexed: 12/24/2022]
Abstract
OBJECTIVE Uremic myopathy is a condition seen in end-stage renal disease (ESRD), characterized by muscle weakness and muscle fatigue, in which the pathophysiology is uncertain. The aim of this study was to assess the role of abnormal serum constituents in ESRD patients by relating them to the excitability properties of the tibialis anterior muscle, at rest and during electrically induced muscle activation, by recording muscle velocity recovery cycles (MVRC) and frequency ramp responses. METHODS Eighteen ESRD patients undergoing hemodialysis were evaluated by blood sample, MVRC, and frequency ramp (before and near the end of dialysis treatment), quantitative electromyography, and nerve conduction studies. Patients were compared to 24 control subjects. RESULTS In patients, muscle relative refractory period, early supernormality, late supernormality after 5 conditioning stimuli, and latency of the last of 15 and 30 frequency ramp pulses were strongly associated with potassium levels (p < 0.01), showing depolarization before and normalization in the end of hemodialysis. CONCLUSIONS In ESRD patients, the muscle membrane is depolarized, mainly due to hyperkalemia. SIGNIFICANCE Since normal muscle fatigue has been attributed to potassium-induced depolarization, it seems likely that this mechanism is also a major cause of the exaggerated muscle fatigue and weakness in ESRD patients.
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Mitake T, Iwatsuki K, Hirata H. Differences in characteristics of carpal tunnel syndrome between male and female patients. J Orthop Sci 2020; 25:843-846. [PMID: 31780367 DOI: 10.1016/j.jos.2019.10.017] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/02/2019] [Revised: 10/05/2019] [Accepted: 10/30/2019] [Indexed: 11/19/2022]
Abstract
BACKGROUND Sex difference is known to be a risk factor of carpal tunnel syndrome. However, sex differences with regard to the clinical presentation of carpal tunnel syndrome have not received much attention. Thus, this study aimed to detect any difference in the characteristics of carpal tunnel syndrome between male and female and thereby add new insights into disease prevention. METHODS A total of 647 patients (male 193 hands and female 454 hands) with carpal tunnel syndrome who underwent endoscopic or open carpal tunnel release were retrospectively reviewed. The average age at time of surgery was 66 years. Clinical and electrophysiological data of all patients were collected. Six medical conditions, including trigger finger, diabetes mellitus, hemodialysis, hyperlipidemia, hypertension, and obesity were also investigated. RESULTS A significant difference was found in the distribution of comorbidities between the male and female groups. Particularly, the prevalence of diabetes mellitus, hemodialysis, and hypertension were significantly higher in the male group than in the female group. Meanwhile, the presence of thenar muscle atrophy was significantly higher in the female group than in the male group. CONCLUSIONS Women are more likely to experience carpal tunnel syndrome even though they have no comorbidities. We suggest that carpal tunnel syndrome especially in male patients may be reduced by early intervention for diabetes mellitus. Prospective studies are needed to validate the causal relationship between diabetes mellitus and carpal tunnel syndrome.
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Affiliation(s)
- Tatsunori Mitake
- Department of Hand Surgery, Nagoya University Graduate School of Medicine, Nagoya, Japan.
| | - Katsuyuki Iwatsuki
- Department of Hand Surgery, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Hitoshi Hirata
- Department of Hand Surgery, Nagoya University Graduate School of Medicine, Nagoya, Japan
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Tu IT, Cheng YS, Mo PC, Hsu HY, Kuo LC, Jou IM, Su FC. Classifying hand sensorimotor functions of the chronic kidney disease patients using novel manual tactile test and pinch-holding-up activity. PLoS One 2019; 14:e0219762. [PMID: 31295337 PMCID: PMC6623959 DOI: 10.1371/journal.pone.0219762] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2019] [Accepted: 07/02/2019] [Indexed: 11/18/2022] Open
Abstract
Hand function deterioration brings about inconvenience to the daily lives of the chronic kidney disease patients. However, a full spectrum of hand function examination is absent. Therefore, this study aimed to classify the hand sensorimotor functions of the chronic kidney disease patients using the novel sensorimotor assessment tools, manual tactile test (MTT) and pinch-holding-up activity (PHUA) test, and explore the feasibility in comparison with traditional evaluations in the clinical practice. 68 stage-5 chronic kidney disease patients and 50 healthy subjects were recruited in this study. A series of conventional evaluations and two novel hand function tools, manual tactile test and pinch-holding-up activity test were conducted from the perspective of hand dexterity, sensory input threshold, force generation and sensorimotor control. Independent t-test was used to find out group differences and the receiver operating characteristic curve was used to determine accuracy of the tests. In our results, significant reduction of hand dexterity, sensory input, force generation and sensorimotor control was found in patients from an overall perspective. This trend was discovered to be the same when dividing the subjects into the old and young age group. From the receiver operator characteristic curves, nearly all the areas under the curve of all tests were over 0.8. The novel evaluation tools, the manual tactile test and pinch-holding-up activity, were found to have comparable or even better accuracy than the traditional ones. The shape and weight subtests of the manual tactile test displayed the highest accuracy. To sum up, by incorporating the novel and conventional assessment tests, this study built up the fundamental understanding of the hand functions in multiple dimensions and consolidate the clinical merits of applying the two novel tools, manual tactile test and pinch-holding-up activity, on chronic kidney disease patients.
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Affiliation(s)
- I-Te Tu
- Department of Biomedical Engineering, National Cheng Kung University, Tainan, Taiwan
- Division of Nephrology, Department of Internal Medicine, Chi Mei Medical Center, Liouying, Tainan, Taiwan
| | - Yu-Shiuan Cheng
- Department of Biomedical Engineering, National Cheng Kung University, Tainan, Taiwan
| | - Pu-Chun Mo
- Department of Biomedical Engineering, National Cheng Kung University, Tainan, Taiwan
| | - Hsiu-Yun Hsu
- Department of Biomedical Engineering, National Cheng Kung University, Tainan, Taiwan
- Department of Occupational Therapy, National Cheng Kung University, Tainan, Taiwan
| | - Li-Chieh Kuo
- Department of Biomedical Engineering, National Cheng Kung University, Tainan, Taiwan
- Department of Occupational Therapy, National Cheng Kung University, Tainan, Taiwan
| | - I-Ming Jou
- Department of Orthopedics, E-Da Hospital, Kaohsiung, Taiwan
| | - Fong-Chin Su
- Department of Biomedical Engineering, National Cheng Kung University, Tainan, Taiwan
- Medical Device Innovation Center, National Cheng Kung University, Tainan, Taiwan
- * E-mail:
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Ezzeldin N, Abdel Galil SM, Said D, Kamal NM, Amer M. Polyneuropathy associated with chronic hemodialysis: Clinical and electrophysiological study. Int J Rheum Dis 2018; 22:826-833. [PMID: 30575307 DOI: 10.1111/1756-185x.13462] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2018] [Revised: 11/15/2018] [Accepted: 11/26/2018] [Indexed: 11/27/2022]
Abstract
AIM To estimate the frequency and pattern of peripheral polyneuropathy (PNP) that may affect patients maintained on hemodialysis. PATIENTS AND METHODS The study was carried out on 60 middle-aged male patients attending the Internal Medicine Department for maintenance hemodialysis. All were subjected to a complete neurological examination. Motor and sensory nerve conduction studies of both lower limbs (the tibial, peroneal and sural nerves) and both upper limbs (median and ulnar nerves), as well as F-wave measurements of both tibial and median nerves, were done. The patients were subdivided clinically into two groups, clinically apparent neuropathy and inapparent groups. Then they were divided according to the types of peripheral neuropathy detected by electrophysiological studies into axonal, demyelinated and mixed polyneuropathy. In addition, they were divided into motor, sensory and sensorimotor groups. RESULTS Polyneuropathy was found clinically presented in 33 (55%) cases, while evident by electrophysiological examination in 100% of the clinically apparent group (33 patients) and evident in 92.5% of the clinically inapparent group (27 patients). The frequency of pathologic electrophysiological parameters was significantly higher in patients with longer duration of hemodialysis. Axonal polyneuropathy is the most prevalent type in those patients. CONCLUSION Peripheral polyneuropathy is a common presentation in patients maintained on hemodialysis. The longer the duration of hemodialysis, the more liability to develop PNP that can be detected earlier by electrodiagnostic studies in the subclinical cases.
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Affiliation(s)
- Nillie Ezzeldin
- Rheumatology and Rehabilitation Department, Faculty of Medicine, Zagazig University, Egypt
| | - Sahar Mahfouz Abdel Galil
- Rheumatology and Rehabilitation Department, Faculty of Medicine, Zagazig University, Egypt.,Medicine Department, College of Medicine, Umm Alqura University, Makkah, Saudi Arabia
| | - Dina Said
- Rheumatology and Rehabilitation Department, Faculty of Medicine, Zagazig University, Egypt
| | - Nafesa Mohamed Kamal
- Internal Medicine Department, Faculty of Medicine, Zagazig University, Zagazig, Egypt
| | - Mona Amer
- Neurology Department, Faculty of Medicine, Zagazig University, Zagazig, Egypt
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Pettersen JA, Singh A. Potentially Reversible Rapid-Onset Weakness: Recognizing Colchicine Toxicity. Am J Med 2018; 131:e59-e60. [PMID: 28916423 DOI: 10.1016/j.amjmed.2017.08.029] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/17/2017] [Accepted: 08/17/2017] [Indexed: 09/30/2022]
Affiliation(s)
- Jacqueline A Pettersen
- Division of Neurology, Department of Medicine, University of British Columbia, Vancouver, British Columbia, Canada; Northern Medical Program, University of Northern British Columbia, Prince George, British Columbia, Canada.
| | - Anurag Singh
- Northern Medical Program, University of Northern British Columbia, Prince George, British Columbia, Canada; Division of Nephrology, Department of Medicine, University of British Columbia, Vancouver, British Columbia, Canada
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Denislic M, Tiric-Campara M, Resić H, Al-Hashel JY, Zorec R, Gojak R, Ravnik J. A neurophysiological study of large- and small-diameter nerve fibers in the hands of hemodialysis patients. Int Urol Nephrol 2015; 47:1879-87. [DOI: 10.1007/s11255-015-1117-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2015] [Accepted: 09/18/2015] [Indexed: 10/23/2022]
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Acevedo LM, Peralta-Ramírez A, López I, Chamizo VE, Pineda C, Rodríguez-Ortiz ME, Rodríguez M, Aguilera-Tejero E, Rivero JLL. Slow- and fast-twitch hindlimb skeletal muscle phenotypes 12 wk after ⅚ nephrectomy in Wistar rats of both sexes. Am J Physiol Renal Physiol 2015; 309:F638-47. [PMID: 26246512 DOI: 10.1152/ajprenal.00195.2015] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2015] [Accepted: 08/03/2015] [Indexed: 11/22/2022] Open
Abstract
This study describes fiber-type adaptations in hindlimb muscles, the interaction of sex, and the role of hypoxia on this response in 12-wk ⅚ nephrectomized rats (Nx). Contractile, metabolic, and morphological features of muscle fiber types were assessed in the slow-twitch soleus and the fast-twitch tibialis cranialis muscles of Nx rats, and compared with sham-operated controls. Rats of both sexes were considered in both groups. A slow-to-fast fiber-type transformation occurred in the tibialis cranialis of Nx rats, particularly in males. This adaptation was accomplished by impaired oxidative capacity and capillarity, increased glycolytic capacity, and no changes in size and nuclear density of muscle fiber types. An oxidative-to-glycolytic metabolic transformation was also found in the soleus muscle of Nx rats. However, a modest fast-to-slow fiber-type transformation, fiber hypertrophy, and nuclear proliferation were observed in soleus muscle fibers of male, but not of female, Nx rats. Serum testosterone levels decreased by 50% in male but not in female Nx rats. Hypoxia-inducible factor-1α protein level decreased by 42% in the tibialis cranialis muscle of male Nx rats. These data demonstrate that 12 wk of Nx induces a muscle-specific adaptive response in which myofibers do not change (or enlarge minimally) in size and nuclear density, but acquire markedly different contractile and metabolic characteristics, which are accompanied by capillary rarefaction. Muscle function and sex play relevant roles in these adaptations.
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Affiliation(s)
- Luz M Acevedo
- Laboratory of Muscular Biopathology, Department of Comparative Anatomy and Pathological Anatomy, Faculty of Veterinary Sciences, University of Cordoba, Cordoba, Spain; Departamento de Ciencias Biomédicas, Facultad de Ciencias Veterinarias, Universidad Central de Venezuela, Maracay, Venezuela
| | - Alan Peralta-Ramírez
- Departament of Animal Medicine and Surgery, University of Cordoba, Spain; Escuela de Medicina Veterinaria, Universidad Nacional Autónoma de Nicaragua, León, Nicaragua; and
| | - Ignacio López
- Departament of Animal Medicine and Surgery, University of Cordoba, Spain
| | - Verónica E Chamizo
- Laboratory of Muscular Biopathology, Department of Comparative Anatomy and Pathological Anatomy, Faculty of Veterinary Sciences, University of Cordoba, Cordoba, Spain
| | - Carmen Pineda
- Departament of Animal Medicine and Surgery, University of Cordoba, Spain
| | | | - Mariano Rodríguez
- Unidad de Investigación y Servicio de Nefrología (Red in Ren), Instituto Sanitario de Investigación Biomédica de Córdoba (IMIBIC), Reina Sofia University Hospital, University of Cordoba, Spain
| | | | - José-Luis L Rivero
- Laboratory of Muscular Biopathology, Department of Comparative Anatomy and Pathological Anatomy, Faculty of Veterinary Sciences, University of Cordoba, Cordoba, Spain;
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Shende VS, Sharma RD, Pawar SM, Waghmare SN. A study of median nerve entrapment neuropathy at wrist in uremic patients. Indian J Nephrol 2015. [PMID: 26199474 PMCID: PMC4495477 DOI: 10.4103/0971-4065.144425] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Carpal tunnel syndrome (CTS) is the most common entrapment neuropathy seen in uremic patients. The study was undertaken to estimate the frequency of CTS in uremic patients and to identify the most sensitive electrodiagnostic test. Study was conducted on 80 subjects of age 30–60 years. End-stage kidney disease patients were recruited for the clinical evaluation, motor nerve conduction studies (NCS), sensory NCS, F wave study and median-versus-ulnar comparison studies (palm-to-wrist mixed comparison study, digit 4 sensory latencies study and lumbrical-interossei comparison study). Among three different diagnostic modalities, frequency of CTS was found to be 17.5% with clinical evaluation, 15% with routine NCS studies and 25% with median-versus-ulnar comparison studies. Among the median-versus-ulnar comparison studies, lumbrical-interossei comparison study was found to be most sensitive (90%). The comparative tests for CTS are more sensitive compared to routine NCS and clinical examination. Among the comparative tests, lumbrical-interossei comparison study is the most sensitive. Early diagnosis of CTS may help patients of uremia to seek proper treatment at an appropriate time.
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Affiliation(s)
- V S Shende
- Department of Physiology, MGIMS, Sevagram, Wardha, Maharashtra, India
| | - R D Sharma
- Department of Physiology, MGIMS, Sevagram, Wardha, Maharashtra, India
| | - S M Pawar
- Department of Physiology, MGIMS, Sevagram, Wardha, Maharashtra, India
| | - S N Waghmare
- Department of Physiology, MGIMS, Sevagram, Wardha, Maharashtra, India
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Neuromuscular issues in systemic disease. Curr Neurol Neurosci Rep 2015; 15:48. [PMID: 26008813 DOI: 10.1007/s11910-015-0565-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
The neuromuscular system can be involved in several systemic conditions. Clinical manifestations can appear at onset or throughout the course of the disease process. New investigational methods, including imaging of peripheral nerves, new laboratory tests, and antibodies, are available. In addition to symptomatic therapies, specific treatment options, such as for familial amyloid neuropathy and Fabry's disease, are becoming increasingly available. Pathomechanisms vary depending on the underlying disease process. In addition to metabolic, hormonal, immune, and antibody-mediated mechanisms, in some generalized diseases, genetic causes need to be considered. This review focuses on different aspects of the peripheral nervous system including the nerve roots, plexuses, mononeuropathies and generalized neuropathies, neuromuscular junction disorders, muscle, and autonomic nervous system.
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Tseng CH, Liao CC, Kuo CM, Sung FC, Hsieh DPH, Tsai CH. Medical and non-medical correlates of carpal tunnel syndrome in a Taiwan cohort of one million. Eur J Neurol 2011; 19:91-7. [PMID: 21631646 DOI: 10.1111/j.1468-1331.2011.03440.x] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
BACKGROUND Carpal tunnel syndrome (CTS), with unclear etiology, is the most common entrapment neuropathy. Its occurrence is related to lots of medical and non-medical conditions with uncertain causality. With a large population, we characterized selected demographical and clinical factors to add more information on CTS-correlated factors and new insight into future CTS prevention. METHODS A national insurance claim dataset of one million enrollees in Taiwan was used to identify 15 802 patients with CTS and 31 604 randomly selected controls, during a period of 7 years starting 1 January 2000. Statistical association with CTS was determined for five sociodemographic and nine medical factors. RESULTS Patients were predominantly women (65.6% vs. 47.7% in the control group) and older (40 and above, 62.6% vs. 36.2%). Rheumatoid arthritis was found to be the most significant comorbidity associated with CTS, followed by gout, hypertension, diabetes, obesity, uremia, and acromegaly. For younger group age ≤39, the association of these comorbidities was stronger, and hypothyroidism and vitamin B(6) deficiency were additional comorbidities. Aging appears to reduce the relative impact of the diseases commonly associated with CTS as the possible risk factors. CONCLUSIONS Identification of the CTS correlates in younger group would be of greater value in timely detection and treatment for these diseases. Correcting these disorders may aid in removing possible causes of CTS. This is the first report on the effect of aging on probable CTS risk factors. How factors associated with aging contribute to the development of CTS remains to be determined.
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Affiliation(s)
- C-H Tseng
- Department of Neurology, China Medical University Hospital, Taichung, Taiwan
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Z'Graggen WJ, Aregger F, Farese S, Humm AM, Baumann C, Uehlinger DE, Bostock H. Velocity recovery cycles of human muscle action potentials in chronic renal failure. Clin Neurophysiol 2010; 121:874-81. [PMID: 20181515 DOI: 10.1016/j.clinph.2010.01.024] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2009] [Revised: 12/20/2009] [Accepted: 01/08/2010] [Indexed: 11/19/2022]
Abstract
OBJECTIVE To test the hypothesis that muscle fibers are depolarized in patients with chronic renal failure, by measuring velocity recovery cycles of muscle action potentials as indicators of muscle membrane potential. METHODS Velocity recovery cycles were recorded from brachioradialis muscle by direct muscle stimulation in 13 patients, before, immediately after, and 1h after haemodialysis, and compared with those from 10 age-matched controls. RESULTS In the patients, supernormality was reduced by 47%, and relative refractory period increased by 60.5% compared with controls (both P<0.001). Dialysis normalized the supernormality, but an hour later it was again reduced. These changes in supernormality were strongly correlated with the changes in serum potassium levels (P<0.0001). A late component of supernormality, attributed to potassium accumulation in the t-tubule system, was also reduced in the patients but remained abnormally low after dialysis. CONCLUSIONS Muscle membranes in the patients were chronically depolarized by hyperkalemia. Whereas dialysis transiently normalized muscle membrane potential, it was not adequate to normalize t-tubule function. SIGNIFICANCE Chronic muscle membrane depolarization by hyperkalemia may account for some of the functional deficits in uremic myopathy. Consistent normalization of membrane potential by avoiding hyperkalemia may therefore reduce symptoms of 'uremic myopathy'.
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Affiliation(s)
- W J Z'Graggen
- Department of Neurology, Inselspital, Bern University Hospital and University of Bern, Switzerland
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