[Early detection by urinary proteome analysis : A new concept in patient management of diabetic nephropathy]. / Früherkennung mittels Urinproteomanalyse : Ein neues Konzept im Patientenmanagement der diabetischen Nephropathie.

BACKGROUND: The early detection and treatment of diabetic nephropathy (DN) is of crucial importance as patients with diabetes mellitus represent the largest proportion of patients on dialysis, with the highest morbidity and mortality. Currently, the first clinical sign of incipient DN is microalbuminuria, but its precision is not optimal. Many studies now report that proteins and peptides are new biomarkers in urine that primarily depict the pathophysiology of DN and thus allow for improved diagnosis of DN. OBJECTIVES: The presentation of new concepts for the early detection and treatment of DN for better patient management. MATERIAL AND METHODS: A systematic literature search was carried out. RESULTS: Many potential markers have been described in the search for new biomarkers to diagnose DN by urinary proteome analysis. However, many of these studies were not meaningful due to the small number of samples. This limitation led to inadequate validation of proteins that could not be confirmed as markers. However, the diagnostic benefit of CKD 273, a multimarker of 273 protein fragments, was sustainably demonstrated for the early diagnosis of DN. This multi-marker shows significant advantages in the precision of diagnosis and prognosis compared to albuminuria. Furthermore, many of its peptide markers map the molecular pathophysiology of DN. CONCLUSIONS: Clinical urinary proteome analysis shows great benefits and is already an appropriate tool for the early detection of incipient DN.

The nephrology eHealth-system of the metropolitan region of Hannover for digitalization of care, establishment of decision support systems and analysis of health care quality.

BACKGROUND: Even though a high demand for sector spanning communication exists, so far no eHealth platform for nephrology is established within Germany. This leads to insufficient communication between medical providers and therefore suboptimal nephrologic care. In addition, Clinical Decision Support Systems have not been used in Nephrology until now. METHODS: The aim of NEPHRO-DIGITAL is to create a eHealth platform in the Hannover region that facilitates integrated, cross-sectoral data exchange and includes teleconsultation between outpatient nephrology, primary care, pediatricians and nephrology clinics to reduce communication deficits and prevent data loss, and to enable the creation and implementation of an interoperable clinical decision support system. This system will be based on input data from multiple sources for early identification of patients with cardiovascular comorbidity and progression of renal insufficiency. Especially patients will be able to enter and access their own data. A transfer to a second nephrology center (metropolitan region of Erlangen-Nuremburg) is included in the study to prove feasibility and scalability of the approach. DISCUSSION: A decision support system should lead to earlier therapeutic interventions and thereby improve the prognosis of patients as well as their treatment satisfaction and quality of life. The system will be integrated in the data integration centres of two large German university medicine consortia (HiGHmed ( highmed.org ) and MIRACUM ( miracum.org )). TRIAL REGISTRATION: ISRCTN16755335 (09.07.2019).

The KTx360°-study: a multicenter, multisectoral, multimodal, telemedicine-based follow-up care model to improve care and reduce health-care costs after kidney transplantation in children and adults.

BACKGROUND: Follow-up care after kidney transplantation is performed in transplant centers as well as in local nephrologist's practices in Germany. However, organized integrated care of these different sectors of the German health care system is missing. This organizational deficit as well as non-adherence of kidney recipients and longterm cardiovascular complications are major reasons for an impaired patient and graft survival. METHODS: The KTx360° study is supported by a grant from the Federal Joint Committee of the Federal Republic of Germany. The study will include 448 (39 children) incident patients of all ages with KTx after study start in May 2017 and 963 (83 children) prevalent patients with KTx between 2010 and 2016. The collaboration between transplant centers and nephrologists in private local practices will be supported by internet-based case-files and scheduled virtual visits (patient consultation via video conferencing). At specified points of the care process patients will receive cardiovascular and adherence assessments and respective interventions. Care will be coordinated by an additional case management. The goals of the study will be evaluated by an independent institute using claims data from the statutory health insurances and data collected from patients and their caregivers during study participation. To model longitudinal changes after transplantation and differences in changes and levels of immunosuppresive therapy after transplantation between study participants and historical data as well as data from control patients who do not participate in KTx360°, adjusted regression analyses, such as mixed models with repeated measures, will be used. Relevant confounders will be controlled in all analyses. DISCUSSION: The study aims to prolong patient and graft survival, to reduce avoidable hospitalizations, co-morbidities and health care costs, and to enhance quality of life of patients after kidney transplantation. TRIAL REGISTRATION: ISRCTN29416382 (retrospectively registered on 05.05.2017).

Impact of Everolimus and Low-Dose Cyclosporin on Cytomegalovirus Replication and Disease in Pediatric Renal Transplantation.

In order to investigate the hypothesis that the mammalian target of rapamycin inhibitor everolimus (EVR) shows anticytomegalovirus (CMV) activity in pediatric patients, we analyzed the impact of EVR-based immunosuppressive therapy on CMV replication and disease in a large cohort (n = 301) of pediatric kidney allograft recipients. The EVR cohort (n = 59), who also received low-dose cyclosporin, was compared with a control cohort (n = 242), who was administered standard-dose cyclosporin or tacrolimus and an antimetabolite, mostly mycophenolate mofetil (91.7%). Multivariate analysis revealed an 83% lower risk of CMV replication in the EVR cohort than in the control cohort (p = 0.005). In CMV high-risk (donor+/recipient-) patients (n = 88), the EVR-based regimen was associated with a significantly lower rate of CMV disease (0% vs. 14.3%, p = 0.046) than the standard regimen. In patients who had received chemoprophylaxis with (val-)ganciclovir (n = 63), the CMV-free survival rates at 1 year and 3 years posttransplant (100%) were significantly (p = 0.015) higher in the EVR cohort (n = 15) than in the control cohort (n = 48; 1 year, 75.0%; 3 years, 63.3%). Our data suggest that in pediatric patients at high risk of CMV, an EVR-based immunosuppressive regimen is associated with a lower risk of CMV disease than a standard-dose calcineurin inhibitor-based regimen.

BK polyomavirus-specific cellular immune responses are age-dependent and strongly correlate with phases of virus replication.

BK polyomavirus (BKPyV) infection is widespread and typically asymptomatic during childhood, but may cause nephropathy in kidney transplant recipients. However, there is only limited knowledge on BKPyV-specific immunity in children and adults, and its role in BKPyV-replication and disease posttransplant. We therefore characterized BKPyV-specific immunity from 122 immunocompetent individuals (1-84 years), 38 adult kidney recipients with (n = 14) and without BKPyV-associated complications (n = 24), and 25 hemodialysis (HD) patients. Blood samples were stimulated with overlapping peptides of BKPyV large-T antigen and VP1 followed by flow-cytometric analysis of activated CD4 T cells expressing interferon-γ, IL-2 and tumor necrosis factor-α. Antibody-levels were determined using enzyme-linked immunosorbent assay. Both BKPyV-IgG levels and BKPyV-specific CD4 T cell frequencies were age-dependent (p = 0.0059) with maximum levels between 20 and 30 years (0.042%, interquartile range 0.05%). Transplant recipients showed a significantly higher BKPyV-specific T cell prevalence (57.9%) compared to age-matched controls (21.7%) or HD patients (28%, p = 0.017). Clinically relevant BKPyV-replication was associated with elevated frequencies of BKPyV-specific T cells (p = 0.0002), but decreased percentage of cells expressing multiple cytokines (p = 0.009). In conclusion, BKPyV-specific cellular immunity reflects phases of active BKPyV-replication either after primary infection in childhood or during reactivation after transplantation. Combined analysis of BKPyV-specific T cell functionality and viral loads may improve individual risk assessment.

Different models of transition to adult care after pediatric kidney transplantation: a comparative study.

Transition from pediatric to adult care is a critical and difficult step for young people with transplants and for the multidisciplinary team involved. In our retrospective study, we investigated the clinical course in a two-yr period of transition. Data from 66 teenagers were collected one yr before and after their transfer to three different adult care settings: (i) a specialized transition clinic, (ii) a general transplantation clinic, and (iii) a nephrologist. Patient survival rate was 100%. Three patients developed graft loss. GFR development was comparable in the three settings (ΔGFR 1.4 ± 8.7 vs. 3.1 ± 10.6 vs. 0.8 ± 4.4 mL/min/1.73 m2 , p = ns). Immunosuppressive therapy was stable in setting 1, whereas the number of changes increased in setting 2 and even more in setting 3. The percentage of patients with steroids increased from 36% to 38% and 52% in settings 1-3. Patient satisfaction was highest in setting 1 (100% vs. 64% and 78%, p < 0.05). Setting 1 was associated with fewer changes in therapy (13% vs. 91% and 45%, p < 0.05). The use of a specialized transition clinic is associated with fewer changes in medication and care and a higher level of patient satisfaction. This was not associated with a lower increase in GFR one yr after transition. Long-term results are awaited.

Growing experience with mTOR inhibitors in pediatric solid organ transplantation.

Controlled trials of mTOR inhibitors in children following solid organ transplantation are scarce, although evidence from prospective single-arm studies is growing. Everolimus with reduced CNI therapy has been shown to be efficacious and safe in de novo pediatric kidney transplant patients in prospective trials. Prospective and retrospective data in children converted from CNI therapy to mTOR inhibition following kidney, liver, or heart transplantation suggest preservation of immunosuppressive efficacy. Good renal function has been maintained when mTOR inhibitors are used de novo in children following kidney transplantation or after conversion to mTOR inhibition with CNI minimization. mTOR inhibition with reduced CNI exposure is associated with a low risk for developing infection in children. Growth and development do not appear to be impaired during low-dose mTOR inhibition, but more studies are required. No firm conclusions can be drawn as to whether mTOR inhibitors should be discontinued in children requiring surgical intervention or whether mTOR inhibition delays progression of hepatic fibrosis after pediatric liver transplantation. In conclusion, current evidence suggests that use of mTOR inhibitors in children undergoing solid organ transplantation is efficacious and safe, but a number of issues remain unresolved and further studies are required.

Ventriculoperitoneal shunts in children on peritoneal dialysis: a survey of the International Pediatric Peritoneal Dialysis Network.

OBJECTIVE: The aim of this study was to inform best evidence-based practice by collating and disseminating the experiences of members of the International Pediatric Peritoneal Dialysis Network with children having concurrent ventriculoperitoneal shunts (VPS) and peritoneal dialysis catheters (PDC). METHODS: An online questionnaire was created and distributed to all 135 centers participating in the International Pediatric Peritoneal Dialysis Network; the overall response rate was 56 %. RESULTS: A total of 18 patients with a concurrent VPS and PDC were reported. The children were 0-12 (mean 6.8) years old at the time of placement of the second indwelling device (PDC or VPS). In 15 cases, the PDC was inserted post-VPS. On average, the two catheters were present concurrently for 23 (range 1-60) months. There were 20 episodes of peritonitis observed in 11 of the 18 patients during a period of 392 months at risk, which is a peritonitis rate of 1/19.6 months. Only one patient developed both a VPS infection and an episode of peritonitis, and these events were temporally unrelated. No episodes of an ascending shunt infection or meningitis occurred in association with any episode of peritonitis, and no other complications of catheter dysfunction were described. CONCLUSIONS: The rate of peritonitis, the absence of any documented ascending or descending infections and the lack of catheter dysfunction during the period of observation suggests that the presence of, or need for, a VPS should not preclude PD as a safe option for children requiring renal replacement therapy.

CXCL13 as a novel marker for diagnosis and disease monitoring in pediatric PTLD.

Posttransplant lymphoproliferative disease (PTLD) is a severe complication of immunosuppressive treatment in organ-grafted children. Early diagnosis of PTLD is hampered by both unspecific clinical symptoms and lack of easy accessible markers. The homeostatic chemokine CXCL13, which plays a crucial role in B-cell homing and lymphoid organ development, is expressed in some lymphomatous diseases. This study aims to investigate whether serum CXCL13 (sCXCL13) levels correlate with occurrence and regression of PTLD in pediatric solid-organ graft recipients. Serum samples from PTLD patients (n = 21), patients with Epstein-Barr virus (EBV) reactivation (n = 18), and healthy age-matched controls (n = 19) were tested for CXCL13 using a commercially available ELISA kit. sCXCL13 levels were significantly higher in PTLD patients than in healthy children. PTLD patients had also higher sCXCL13 values than pediatric solid-organ recipients with EBV reactivation. An increase in sCXCL13 levels was observed from EBV reactivation to PTLD diagnosis in most cases. Elevated sCXCL13 levels were detected up to 2 years prior to PTLD diagnosis and correlated well with response to cytoreductive treatment in individual patients. sCXCL13, thus, may be a readily available surrogate marker for the diagnosis of PTLD and for monitoring of response to treatment in patients with initially elevated sCXCL13 levels.

De novo therapy with everolimus, low-dose ciclosporine A, basiliximab and steroid elimination in pediatric kidney transplantation.

The number of acute rejections and infections after pediatric kidney transplantation (KTX) could not be reduced in the last years. To reduce these events, we investigated a new immunosuppressive protocol in a prospective trial. After KTX, 20 children (median age 12 years, range 1-17) were initially treated with Basiliximab, ciclosporine A (CsA) (trough-level = C0 200-250 ng/mL) and prednisolone. After 2 weeks, CsA dose was reduced to 50% (C0 75-100 ng/mL, after 6 months: 50-75 ng/mL) and everolimus (1.6 mg/m²) /day) was started (C0 3-6 ng/mL). Six months after KTX prednisolone was set to alternate dose and stopped 3 months later. All 20 protocol biopsies 6 months after KTX showed no acute rejection or borderline findings. Indication biopsies resulted in no acute rejections and two borderline findings. Mean glomerular filtration rate (GFR) 1 year after KTX was 71 ± 25 mL/min/1.73 m². Without cytomegalovirus (CMV)-prophylaxis, only two primary CMV infections were seen despite a donor/recipient-CMV-constellation pos./neg. in 10/20 children. In pediatric KTX, de novo immunosuppression with low-dose CsA, everolimus and steroid withdrawal after 9 months led to promising results according to numbers of acute rejections and infections. Further follow up is needed. Future larger trials will have to confirm our findings.

Protocol biopsy-driven interventions after pediatric renal transplantation.

The therapeutic value of protocol biopsies (PBs) in renal transplant recipients remains unclear. We performed protocol biopsies in 57 children six months after transplantation. We increased the CNI dose in patients with borderline findings. In cases of Banff grade Ia, six prednisolone IV-pulses were given and the CNI dose was increased. CNI toxicity and polyomavirus nephropathy led to a reduction in the CNI dose. GFR was compared with a control group of 51 children with no PBs transplanted in the same period. Forty-two percent of PBs had no pathological changes, 24% IF/TA. Borderline findings were detected in 11%, Banff grade Ia in 15% (CNI), toxicity in 8%, and one case showed polyomavirus nephropathy. GFR after 1.5 and 2.5 yr was similar in both groups. GFR 3.5 yr after transplantation was significantly higher in the intervention group (57 ± 17 vs. 46 ± 20). Patients treated with low-dose CNI and everolimus had a significantly lower number of pathological findings in PBs. The performance of protocol biopsies followed by a standardized treatment algorithm led to better graft function 3.5 yr after transplantation. Prospective randomized studies to confirm our findings are needed.

A U3 small nuclear ribonucleoprotein-requiring processing event in the 5' external transcribed spacer of Xenopus precursor rRNA.

A processing site has been identified within the 5' external transcribed spacer (ETS) of Xenopus laevis and X. borealis pre-RNAs, and this in vivo processing can be reproduced in vitro. It involves a stable and specific association of the pre-rRNA with factors in the cell extract, including at least four RNA-contacting polypeptides, yielding a distinct complex that sediments at 20S. Processing also requires the U3 small nuclear RNA. This processing, at residue +105 of the 713-nucleotide X. laevis 5' ETS, is highly reminiscent of the initial processing cleavage of mouse pre-rRNA within its 3.5-kb 5' ETS, previously thought to be mammal specific. The frog and mouse processing signals share a short essential sequence motif, and mouse factors can faithfully process the frog pre-rRNA. This conservation suggests that this 5' ETS processing site serves an evolutionarily selective function.

The Xenopus ribosomal DNA 60- and 81-base-pair repeats are position-dependent enhancers that function at the establishment of the preinitiation complex: analysis in vivo and in an enhancer-responsive in vitro system.

Although it is generally believed that the 60- and 81-base-pair (60/81-bp) repeats of the Xenopus laevis ribosomal DNA (rDNA) spacer are position-independent transcriptional enhancers, this has not been shown directly. We have now developed a critical assay which proves that the 60/81-bp repeats do, in fact, stimulate transcription from promoters in cis and that they function in both orientations and when up to 1 kilobase pair from the initiation site. However, contrary to the widely accepted view, these elements are found to be highly position dependent, for they have no net effect when downstream of the initiation site within the transcribed region and they behave as transcriptional silencers of promoters in cis when moved greater than 2 kilobase pairs upstream of the initiation site. The 60/81-bp elements therefore are position-dependent 5' enhancers. We also found that this rDNA enhancer was polymerase I specific and that it was composed of duplicated, individually functional elements. Finally, we report an in vitro system that reproduces both cis enhancement and trans competition by the 60/81-bp repeats. Sequential-addition studies in this system demonstrated that the rDNA enhancer functions in trans at or before establishment of the stable transcription complex, not subsequently at each round of transcription.

Enhancers for RNA polymerase I in mouse ribosomal DNA.

The intergenic spacer of the mouse ribosomal genes contains repetitive 140-base-pair (bp) elements which we show are enhancers for RNA polymerase I transcription analogous to the 60/81-bp repetitive enhancers (enhancers containing a 60-bp and an 81-bp element) previously characterized from Xenopus laevis. In rodent cell transfection assays, the 140-bp repeats stimulated an adjacent mouse polymerase I promoter when located in cis and competed with it when located in trans. Remarkably, in frog oocyte injection assays, the 140-bp repeats enhanced a frog ribosomal gene promoter as strongly as did the homologous 60/81-bp repeats. Mouse 140-bp repeats also competed against frog promoters in trans. The 140-bp repeats bound UBF, a DNA-binding protein we have purified from mouse extracts that is the mouse homolog of polymerase I transcription factors previously isolated from frogs and humans. The DNA-binding properties of UBF are conserved from the mouse to the frog. The same regulatory elements (terminators, gene and spacer promoters, and enhancers) have now been identified in both a mammalian and an amphibian spacer, and they are found in the same relative order. Therefore, this arrangement of elements probably is widespread in nature and has important functional consequences.

Growth in children after kidney transplantation with living related donor graft or cadaveric graft.

The extent to which growth after renal transplantation differs between children with a living related donor graft (LRD) and those with a cadaveric donor graft (CAD) is unclear. We retrospectively studied growth in the 5 years after transplantation in 30 boys who received LRD and 21 who received CAD. Height was similar in both groups after transplantation but was greater in LRD than in CAD recipients during follow-up. LRD recipients were taller at all ages, and had greater growth velocity in infancy and during puberty. Glomerular filtration rate (GFR) was higher immediately after transplantation in LRD than in CAD recipients, but did not differ between the groups during follow-up. GFR and other factors did not affect height 5 years after transplantation. These findings support use of LRD as the preferred option in children.

Living related kidney donation as an advantage for growth of children independent of glomerular filtration rate.

Seventy-two pediatric kidney recipients of living related donors (LRD) and 145 of cadaveric donors (CAD) were analyzed for height standard deviation scores (Ht-SDS) and glomerular filtration rates (GFR) directly after transplantation and over the following 5 years. GFR was significantly higher immediately after transplantation in LRD compared with CAD recipients; however, GFR was not different during the 5-year follow-up period. Although Ht-SDS was comparable at the time of transplantation in both groups, it was significantly higher among LRD recipients over the next 5 years. Multivariate and covariate analyses showed that Ht-SDS after 5 years was mainly influenced only by CAD vs LRD and not by GFR or other factors, namely, donor age, rejections, time of dialysis, preemptive transplantation, age at transplantation, or immunosuppression. Thus, children receiving grafts from LRD showed a better catch-up growth independent of the GFR than those after CAD transplantation. We concluded that the period of donor death and prolonged cold ischemia in CAD grafts may lead to changes in gene expression of cytokines and other mediator molecules that affect bone metabolism. Better growth seems to be an additional factor supporting the policy of LRD kidney transplantation as the best option in children.

FRAIL-NH Predicts Outcomes in Long Term Care.

BACKGROUND/OBJECTIVES: To investigate the predictive validity of the short, simple FRAIL-NH frailty screening tool in the long term care population and to then compare the predictive validity with the frailty index (FI) for 6-month adverse health outcomes. DESIGN: Retrospective study using the Minimum Data Set (MDS) 3.0 and chart review from June-December 2014. SETTING: Two Long Term Care Facilities in Saint Louis, MO. PARTICIPANTS: 270 patients ages ≥ 65 years old residing in long term care. MEASUREMENTS: Frailty was measured using the FRAIL-NH and Frailty Index (FI) criteria. Adverse outcomes measured at 6-month follow-up included falls, hospitalizations, and hospice enrollment/mortality. RESULTS: Based on screening tool used frailty prevalence was 48.7% for FRAIL-NH and 30.3% for FI. The FRAIL-NH pre-frail (Adjusted Odds Ratio [AOR]=2.62; 95% Confidence Interval [CI]=1.25-5.54; p=0.11) classification was associated with 6 month risk of falling and mortality/hospice enrollment was associated with the frail classification, AOR=3.96 (1.44-10.87, p=0.007). Combining the pre-frail and frail categories both measures predicted 6 month mortality with the FRAIL-NH being the strongest predictor (AOR=3.36; 95%CI=1.26-8.98; p=0.016) and the FI was a more modest predictor with an AOR of 2.28; 95%CI=1.01-5.15; p=0.047. When directly comparing the FRAIL-NH to the FI, the FRAIL-NH pre-frail were at increased risk of falling, AOR=2.42 (1.11-5.92, p=0.027) and the FRAIL-NH frail were at increased risk of hospice enrollment/death, OR=3.25 (1.04- 10.86) p=0.044. CONCLUSION: In comparison to the FI, the FRAIL-NH preformed just as well at screening for frailty and was a slightly better predictor of adverse outcomes. The FRAIL-NH is a brief, easy-to-administer frailty screening tool appropriate for long term care patients and predicts increased risk of falls in the pre-frail and mortality/hospice enrollment in the frail.

Effect of extracellular Ca2+, K+ and OH- on erythrocyte membrane potential as monitored by the fluorescent probe 3,3'-dipropylthiodicarbocyanine.

Changes in fluorescence intensity of thiodicarbocyanine, DiS-C3(5), were correlated with direct microelectrode potential measurements in red blood cells from Amphiuma means and applied qualitatively to evaluate the effects of extracellular Ca2+, K+ and pH on the membrane potential of human red cells. Increasing extracellular [Ca2+] from 1.8 to 15 mM causes a K+-dependent hyperpolarization and decrease in fluorescence intensity in Amphiuma red cells. Both the hyperpolarization and fluorescence change disappear when the temperature is raised from 17 to 37 degrees C. No change in fluorescence intensity is observed in human red cells with comparable increase in extracellular Ca2+ in the temperature range 5-37 degrees C. Increasing the extracellular pH, however, causes human red cells to respond to an increase in extracellular Ca2+ with a significant but temporary loss in fluorescence intensity. This effect is blocked by EGTA, quinine or by increasing extracellular [K+], indicating that at elevated extracellular pH, human erythrocytes respond to an increase in extracellular Ca2+ with an opening of K+ channels and associated hyperpolarization of the plasma membrane.

A calmodulin activated Ca2+-dependent K+ channel in human erythrocyte membrane inside-out vesicles.

The role of calmodulin in stimulating active calcium transport in the human red cell membrane is well documented. In contrast, efforts to characterize the effect of calmodulin on the Ca2+-dependent K+ channel in erythrocyte membranes have given rise to conflicting reports. These studies have indicated that experimental conditions may play a critical role in preserving the Ca2+-dependent K+ channels in erythrocyte inside-out vesicles. With these observations in mind, a double-labelling study of simultaneous active Ca2+ and passive Rb+ uptake in red-cell inside-out vesicles was undertaken. Addition of calmodulin and ATP to a suspension of inside-out vesicles containing 1 mM K+ caused a Ca2+-dependent increase in both the rate of active calcium transport and Rb+ uptake. The initial Rb+ isotope flux was increased 3-fold over the rate observed in the absence of calmodulin. The k1/2 for activation of K+ permeability was approx. 5 X 10(-7) M Ca2+ as compared to 10(-6) M Ca2+ for active Ca2+ transport. Addition of the calmodulin antagonists pimozide and chlorpromazine blocked calmodulin activation of the Ca2+-dependent K+ channel. The observation that activation of the K+ channel occurs at Ca2+ concentrations which are lower than those required for maximum stimulation of the calcium pump suggests that these processes are dependent on two states of the calmodulin molecule, characterized by a lower or higher amount of Ca2+ bound to calmodulin.

Effect of antihistamines and chlorpromazine on the calcium-induced hyperpolarization of the Amphiuma red cell membrane.

1. It has previously been demonstrated that an increase in extracellular Ca2+ conce-tratio- induces a trandient increase in K+ permeability and associated hyperpolarization of the red cell membrane of the giant salamander, Amphiuma meand. This phenomenon is analogous to the Ca2+-induced KCl loss observed in ATP-depleted human red cells and red cell ghosts. 2. Histamine, which enhances the Ca2+-induced K+ loss from depleted human red cells, is without effect on this Ca2+-induced hyperpolarization of Amphiuma red cells. 3. Promethazine (10 muM) and mepyramine (1 mM), which inhibit the Ca2+-induced K+ loss in depleted human red cells, also block the Ca2+-related hyperpolarization of Amphiuma erythrocytes. 4. Chlorpromazine (25 muM), despite being a weak antihistamine, is equally effective in blocking the Ca2+-induced hyperpolarization of Amphiuma red cells. 5. Ionophore A23187 causes a large and sustained Ca2+/K+-dependent hyperpolarization even in the presence of normal (1.8 mM) concentrations of Ca2+. This hyperpolarization is relatively insensitive to chlorpromazine and promethazine. 6. The inhibition of the Ca2+-induced hyperpolarization of the Amphiuma red cell membrane by chlorpromazine and promethazine may berelated to their properties as local anaesthetics.