Light Chain Deposition Disease Recurrence in Renal Allograft after Long-Term Remission.

Light chain deposition disease (LCDD) is a rare manifestation of monoclonal gammopathy, which can lead to renal failure. We previously reported a detailed recurrence process in a case of LCDD after renal transplantation. To the best of our knowledge, no report has described the long-term clinical course and renal pathology findings of recurrent LCDD in patients after renal transplantation. In this case report, we describe the long-term clinical presentation and changes in renal pathology of the same patient after early LCDD relapse in a renal allograft. A 54-year-old woman with recurrent immunoglobulin A λ-type LCDD in an allograft was admitted 1 year post-transplant for bortezomib and dexamethasone therapy. At 2 years post-transplantation, a graft biopsy performed after complete remission was achieved, showing some glomeruli with residual nodular lesions similar to the pre-treatment renal biopsy findings. However, the enlarged subendothelial space disappeared. She remained in complete remission serologically for 6 years. Subsequently, the ratio of serum κ/λ-free light chains decreased gradually. She underwent a transplant biopsy approximately 12 years after renal transplantation due to increased proteinuria and decreased renal function. Compared with the previous graft biopsy, almost all glomeruli showed advanced nodule formation and subendothelial expansion. Because the LCDD case relapsed after long-term remission following renal transplantation, protocol biopsy monitoring might be necessary.

Study of Glomerulopathy in Donors after Kidney Transplantation.

INTRODUCTION: Living kidney donation improves the lives of individuals with kidney failure; however, recent studies have suggested that living kidney donors may be at a relatively higher risk of reduced renal function than healthy non-donors. We therefore aimed to evaluate the clinical and pathological findings in living kidney donors who developed kidney disease. METHODS: From January 1991 to May 2019, 1,625 live kidney donations were performed at our hospital. Among the donors, 7 developed kidney disease after donation and underwent open renal biopsy. We studied the clinical and pathological findings of these patients from their clinical records. RESULTS: There were 3 patients with immunoglobulin A (IgA) nephropathy, 2 with membranous nephropathy, 1 with anti-neutrophil cytoplasmic antibody (ANCA)-associated glomerulonephritis, and 1 with secondary focal segmental glomerulosclerosis (FSGS). All patients with IgA nephropathy had latent IgA deposition on their baseline biopsy. One patient with membranous nephropathy demonstrated findings of membranous nephropathy on the baseline biopsy, despite being asymptomatic. All patients, except for those with ANCA-associated nephropathy and secondary FSGS, recovered from the nephritis or maintained an adequate renal function after treatment. DISCUSSION/CONCLUSION: Baseline biopsy is necessary for assessing the renal condition of kidney donors, and these donors require long-term follow-up based on their baseline biopsy findings. If donors develop kidney disease, appropriate diagnosis and treatment are essential.

Effect of Oral Alfacalcidol on Clinical Outcomes in Patients Without Secondary Hyperparathyroidism Receiving Maintenance Hemodialysis: The J-DAVID Randomized Clinical Trial.

Importance: Patients with chronic kidney disease have impaired vitamin D activation and elevated cardiovascular risk. Observational studies in patients treated with hemodialysis showed that the use of active vitamin D sterols was associated with lower risk of all-cause mortality, regardless of parathyroid hormone levels. Objective: To determine whether vitamin D receptor activators reduce cardiovascular events and mortality in patients without secondary hyperparathyroidism undergoing hemodialysis. Design, Setting, and Participants: Randomized, open-label, blinded end point multicenter study of 1289 patients in 207 dialysis centers in Japan. The study included 976 patients receiving maintenance hemodialysis with serum intact parathyroid hormone levels less than or equal to 180 pg/mL. The first and last participants were enrolled on August 18, 2008, and January 26, 2011, respectively. The final date of follow-up was April 4, 2015. Interventions: Treatment with 0.5 µg of oral alfacalcidol per day (intervention group; n = 495) vs treatment without vitamin D receptor activators (control group; n = 481). Main Outcomes and Measures: The primary outcome was a composite measure of fatal and nonfatal cardiovascular events, including myocardial infarctions, hospitalizations for congestive heart failure, stroke, aortic dissection/rupture, amputation of lower limb due to ischemia, and cardiac sudden death; coronary revascularization; and leg artery revascularization during 48 months of follow-up. The secondary outcome was all-cause death. Results: Among 976 patients who were randomized from 108 dialysis centers, 964 patients were included in the intention-to-treat analysis (median age, 65 years; 386 women [40.0%]), and 944 (97.9%) completed the trial. During follow-up (median, 4.0 years), the primary composite outcome of cardiovascular events occurred in 103 of 488 patients (21.1%) in the intervention group and 85 of 476 patients (17.9%) in the control group (absolute difference, 3.25% [95% CI, -1.75% to 8.24%]; hazard ratio, 1.25 [95% CI, 0.94-1.67]; P = .13). There was no significant difference in the secondary outcome of all-cause mortality between the groups (18.2% vs 16.8%, respectively; hazard ratio, 1.12 [95% CI, 0.83-1.52]; P = .46). Of the 488 participants in the intervention group, 199 (40.8%) experienced serious adverse events that were classified as cardiovascular, 64 (13.1%) experienced adverse events classified as infection, and 22 (4.5%) experienced malignancy-related serious adverse events. Of 476 participants in the control group, 191 (40.1%) experienced cardiovascular-related serious adverse events, 63 (13.2%) experienced infection-related serious adverse events, and 21 (4.4%) experienced malignancy-related adverse events. Conclusions and Relevance: Among patients without secondary hyperparathyroidism undergoing maintenance hemodialysis, oral alfacalcidol compared with usual care did not reduce the risk of a composite measure of select cardiovascular events. These findings do not support the use of vitamin D receptor activators for patients such as these. Trial Registration: UMIN-CTR Identifier: UMIN000001194.

Exit Site Infection due to Mycobacterium chelonae in an Elderly Patient on Peritoneal Dialysis.

Nontuberculous mycobacteria (NTM) are rarely isolated from peritoneal dialysis (PD)-associated catheter infections. However, NTM infection is usually difficult to treat and leads to catheter loss. Prompt diagnosis is essential for appropriate treatment. A 70-year-old Japanese man who had been on PD for 2 years and with a medical history of 2 episodes of exit site infections (ESIs) due to methicillin-resistant Staphylococcus aureus was admitted to the hospital due to suspected ESI recurrence. However, Gram staining of the pus revealed no gram-positive cocci. Instead, weakly stained gram-positive rods were observed after 7 days of incubation, which were also positive for acid-fast staining. Rapidly growing NTM Mycobacterium chelonae was isolated on day 14. Despite administering a combination antibiotic therapy, ESI could not be controlled, and catheter removal surgery was performed on day 21. Although PD was discontinued temporarily, the patient did not require hemodialysis, without any uremic symptoms. The catheter was reinserted on day 48, and PD was reinitiated on day 61. The patient was discharged on day 65. Antibiotic therapy was continued for 3 months after discharge, with no indications of recurrent infections observed. It is important to consider the risk of NTM infections in patients on PD. Acid-fast staining could be a key test for prompt diagnosis and provision of an appropriate treatment.

Severe refractory TAFRO syndrome requiring continuous renal replacement therapy complicated with Trichosporon asahii infection in the lungs and myocardial infarction: an autopsy case report and literature review.

BACKGROUND: TAFRO (thrombocytopenia, anasarca, fever, reticulin myelofibrosis/renal failure, and organomegaly) syndrome is a systemic inflammatory disorder and unique clinicopathological variant of idiopathic multicentric Castleman disease that was proposed in Japan. Prompt diagnosis is critical because TAFRO syndrome is a progressive and life threating disease. Some cases are refractory to immunosuppressive treatments. Renal impairment is frequently observed in patients with TAFRO syndrome, and some severe cases require hemodialysis. Histological evaluation is important to understand the pathophysiology of TAFRO syndrome. However, systemic histopathological evaluation through autopsy in TAFRO syndrome has been rarely reported previously. CASE PRESENTATION: A 46-year-old Japanese man with chief complaints of fever and abdominal distension was diagnosed with TAFRO syndrome through imaging studies, laboratory findings, and pathological findings on cervical lymph node and bone marrow biopsies. Interleukin (IL)-6 and vascular endothelial growth factor (VEGF) levels were remarkably elevated in both blood and ascites. Methylprednisolone (mPSL) pulse therapy was initiated on day 10, followed by combination therapy with PSL and cyclosporine A. However, the amount of ascites did not respond to the treatment. The patient became anuric, and continuous renal replacement therapy was initiated from day 50. However, the patient suddenly experienced cardiac arrest associated with myocardial infarction (MI) on the same day. Although the emergent percutaneous coronary intervention was successfully performed, the patient died on day 52, despite intensive care. Autopsy was performed to ascertain the cause of MI and to identify the histopathological characteristics of TAFRO syndrome. CONCLUSIONS: Bacterial peritonitis, systemic cytomegalovirus infection, and Trichosporon asahii infection in the lungs were observed on autopsy. In addition, sepsis-related myocardial calcification was suspected. Management of infectious diseases is critical to reduce mortality in patients with TAFRO syndrome. Although the exact cause of MI could not be identified on autopsy, we considered embolization by fungal hyphae as a possible cause. Endothelial injury possibly caused by excessive secretion of IL-6 and VEGF contributed to renal impairment. Fibrotic changes in anterior mediastinal fat tissue could be a characteristic pathological finding in patients with TAFRO syndrome.

Successful Recovery from Spontaneous Spinal Epidural Hematoma in a Patient Undergoing Hemodialysis.

BACKGROUND Spontaneous spinal epidural hematoma (SSEH) occurs in the spinal epidural space in the absence of traumatic or iatrogenic causes, and is considered to be a neurological emergency, as spinal cord compression may lead to neurological deficit. Prompt diagnosis of SSEH can be difficult due to the variety of presenting symptoms, which may resemble those of stroke. Patients who undergo hemodialysis (HD) are at risk of bleeding due to anticoagulation during dialysis and uremia. However, SSEH in HD patients undergoing HD has rarely been reported. CASE REPORT A 70-year-old Japanese man, who has been undergoing maintenance HD for the previous three years, was admitted to Kariya Toyota General Hospital, Aichi, Japan, with acute chest and abdominal pain, and with complete paraplegia. The patient denied any recent trauma or medical procedures. Magnetic resonance imaging showed an extensive hematoma in the thoracic and lumbar epidural space, extending from T8 to L5. The patient's symptoms improved within three hours following hospital admission, and after three days without HD treatment, the SSEH decreased in size, and the patient successfully recovered without residual neurological deficits and without requiring surgery. CONCLUSIONS The management of SSEH in patients undergoing HD can be difficult, due to anticoagulation during dialysis and uremia. Prompt diagnosis and close neurological monitoring are important for appropriate management. In patients whose symptoms improve within a short period, conservative management may be considered.

[Comparison of benefits to non-dialysis CKD patients between darbepoetin alpha and epoetin beta pegol].

BACKGROUND: Erythropoiesis-stimulating agents (ESAs) are the mainstay of treatment for renal anemia in chronic kidney disease (CKD) patients. However, the difference in hematopoietic effect between darbepoetin alfa (DA) and continuous erythropoiesis receptor activator (CERA) has remained unclear in non-dialysis CKD patients. Another purpose of this study was to analyze the red blood cells indices under treatment with these two ESAs in ESA-naïve CKD patients. METHODS: This study was designed as a multicenter retrospective observational investigation, and included 61 patients receiving DA (group DA) and 36 patients receiving CERA (group CERA) for at least six months. Relative effect of these ESAs was determined by comparing means of the individual monthly average of the area under the curve above the initial level of hemoglobin (Hb), hematocrit (Hct), and red blood cell count (RBC) with the trapezoidal rule, which are maintenance ratios. Serial changes in mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), and mean corpuscular hemoglobin concentration (MCHC) were also evaluated. RESULTS: No differences were found in the mean ratios of Hb, Hct, and RBC, and maintenance ratios of these parameters. The ratio of MCH in group CERA was decreased compared with that in group DA. Subsequent decrease in MCV was also remarkable in group CERA. CONCLUSIONS: It is speculated that iron demand increased during the administration of CERA, which was suggested by changes in the red cell indices. Reticulocyte indices and iron-related parameters could provide a more detailed explanation and the significance of iron supplementation during administration of CERA should be clarified when compared with other types of ESA.

Coronary microvascular function is independently associated with left ventricular filling pressure in patients with type 2 diabetes mellitus.

BACKGROUND: Left ventricular (LV) diastolic dysfunction is known as an early marker of myocardial alterations in patients with diabetes. Because microvascular disease has been regarded as an important cause of heart failure or diastolic dysfunction in diabetic patients, we tested the hypothesis that coronary flow reserve (CFR), which reflects coronary microvascular function, is associated with LV diastolic dysfunction in patients with type 2 diabetes. METHODS: We studied asymptomatic patients with type 2 diabetes but without overt heart failure. Transthoracic Doppler echocardiography was performed that included pulsed tissue Doppler of the mitral annulus and CFR of the left anterior descending artery (induced by adenosine 0.14 mg/kg/min). The ratio of mitral velocity to early diastolic velocity of the mitral annulus (E/e') was used as a surrogate marker of diastolic function. We also evaluated renal function, lipid profile, parameters of glycemic control and other clinical characteristics to determine their association with E/e'. Patients with LV ejection fraction <50%, atrial fibrillation, valvular disease, regional wall motion abnormality, renal failure (serum creatinine >2.0 mg/dl) or type 1 diabetes were excluded. Patients with a CFR <2.0 were also excluded based on the suspicion of significant coronary artery stenosis. RESULTS: We included 67 asymptomatic patients with type 2 diabetes and 14 non-diabetic controls in the final study population. In univariate analysis, age, presence of hypertension, LV mass index, estimated glomerular filtration rate and CFR were significantly associated with E/e'. Multivariate analysis indicated that both LV mass index and CFR were independently associated with E/e'. In contrast, there were no significant associations between parameters of glycemic control and E/e'. CONCLUSIONS: CFR was associated with LV filling pressure in patients with type 2 diabetes. This result suggests a possible link between coronary microvascular disease and LV diastolic function in these subjects.

Patients with adult minimal change nephrotic syndrome treated with long-term cyclosporine did not experience a reduction in their eGFR.

BACKGROUND: The long-term efficacy and safety of cyclosporine (CyA) in the treatment of adult minimal change nephrotic syndrome (MCNS) was examined. METHODS: The medical record of 15 patients diagnosed with MCNS by renal biopsy and treated with CyA for at least 2 years were reviewed. RESULTS: The mean administration period of CyA was 78.3 months. The mean CyA dose for the induction period was 2.1 ± 0.9 mg/kg and 1.7 ± 1.0 mg/kg for the maintenance period. The mean dose of prednisolone used during the induction period was 20.3 mg and 2.7 mg during the maintenance. The frequency of MCNS relapse was decreased to 0.5 times/year in patients treated with CyA, compared to treatment without CyA (2.4 times/y). Two cases of mild liver damage and 3 cases of elevated blood pressure were observed during the administration of CyA. These adverse effects improved after reducing the CyA dose or treatment with an antihypertensive agent. A decrease in the estimated glomerular filtraion rate (eGFR) was not associated with long-term CyA use. CONCLUSION: At our institution, patients who were treated for MCNS with CyA for at least 2 years experienced no deterioration in renal function.

Cetuximab-induced nephrotic syndrome in a case of metastatic rectal cancer.

Proteinuria is common adverse effect that occurs after the use of bevacizumab, but it occurs rarely during administration of cetuximab. We report the first case of nephrotic syndrome induced by cetuximab after completing mFOLFOX6 with bevacizumab followed by sLV5FU2 with bevacizumab for metastatic rectal cancer. Prior to the administration of cetuximab, the patient had never presented proteinuria. After the completion of the loading (400 mg/m(2)) and two subsequent maintenance (250 mg/m(2)) infusions of cetuximab, edema of the lower extremities occurred concomitantly with facial acneiform rash. Based on the laboratory data, diagnosis of nephrotic syndrome was made and secondary diseases of nephrotic syndrome were excluded. Oral administration of prednisolone (0.6 mg/kg/day) was initiated, resulting in no response. The trigger of nephrotic syndrome other than cetuximab was not suggested and attention on occurrence of proteinuria must be devoted to this medicine.

Successful treatment of serial opportunistic infections including disseminated nocardiosis and cryptococcal meningitis in a patient with ANCA-associated vasculitis.

We herein present a case of serial opportunistic infections that included disseminated nocardiosis and cryptococcal meningitis in a 67-year-old man who was diagnosed with ANCA-associated vasculitis and treated with corticosteroids. Upon admission, the initial manifestations of the disease included subcutaneous tumors and multiple lesions in the brain and lungs. Nocardia farcinica was identified in a culture of the aspirated pus. The patient was successfully treated for disseminated nocardiosis with antibiotics. However, three months after discharge, he was hospitalized with complaints of nuchal pain. Cryptococcus neoformans was identified on a culture of the cerebrospinal fluid. Anti-fungal treatment resulted in the remission of cryptococcal meningitis.

A case of diffuse endocapillary proliferative glomerulonephritis associated with polymyalgia rheumatica.

A 70-year-old man complained of muscle pain in his neck, shoulders and pelvic girdle. Proteinuria and hematuria subsequently developed. Blood analysis showed increased acute phase reactants. The histology of renal biopsy showed diffuse endocapillary proliferative glomerulonephritis. There were no signs of autoimmune diseases, malignancies and bacterial or viral infections. His extrarenal symptoms and the results of blood analysis fulfilled three different criteria of polymyalgia rheumatica (PMR). Therefore, diffuse endocapillary proliferative glomerulonephritis associated with PMR was diagnosed. After low-dose prednisolone (10 mg/day) treatment, the muscle pain disappeared, acute phase reactants decreased and hematuria and proteinuria improved. The renal complication of PMR is rare but important to be considered early in the right clinical context.

Reduced hydration status characterized by disproportionate elevation of blood urea nitrogen to serum creatinine among the patients with cerebral infarction.

The significance of fluid metabolism among the patients with cerebral infarction has barely mentioned in the literature despite the several reports suggesting the potential risk of reduced hydration status for the development of cerebral infarction. The aim of the this study is to explore the validity of the presumable relationship between hydration status and cerebral infarction. Ninety-seven patients with cerebral infarction from April 1, 2008 to March 31, 2009 were retrospectively investigated, and their hydration status were evaluated by using several clinical parameters such as a blood urea nitrogen to serum creatinine (BUN/Cr) ratio of >25 and plasma osmolality. Subjects with active infection, congestive heart failure, hepatic failure, gastrointestinal bleeding, or a malignancy were excluded since these conditions should modulate the absolute value of BUN/Cr ratio without a change in hydration status. Twenty-eight patients (29%) were considered as having reduced hydration status. The BUN/Cr ratio decreased significantly after the initiation of medical support (median 21.3; IR: 18.1-24.6), including oral or parenteral fluid supplementation, in comparison to the values at the time of patient admission (median 30.0; IR: 26.8-40.7; p<0.0001). Similar decreases were also observed in the hematocrit, hemoglobin, and plasma osmolality. The group considered to have reduced hydration status had a significantly higher prevalence of cardioembolic stroke than the other subjects. The hydration status may be a contributing factor to subtypes of cerebral infarction. Whether our findings are also the case with overall patients with cerebral infarction should be evaluated in greater detail.

Nephrotic syndrome and renal failure in a patient with metastatic breast cancer.

This report presents a case of nephrotic syndrome and renal failure that developed in a 53-year-old female with metastatic breast carcinoma. She was diagnosed to have osteolytic bone metastases 5 years prior to admission, and had been administered pamidronate with a total dose of approximately 6800 mg. A renal biopsy revealed tubulointerstitial damage and marked wrinkling and retraction of the glomerular basement membrane with hypertrophy and hyperplasia of the epithelial cells, compatible with the collapsing form of focal segmental glomerulosclerosis (FSGS). Despite the discontinuation of pamidronate after admission, her renal function gradually decreased. She was finally managed with continuous palliative care for advanced malignancy through a shared effort, and died 96 days after undergoing the renal biopsy. Although the clinical impact of the pamidronate-associated kidney injury on the longitudinal changes in renal function remains to be delineated, it is therefore reasonable to consider that the collapsing FSGS associated with tubulointerstitial damage may have resulted in the irreversible renal injuries that were observed in the current case. Further studies and accumulated experience with renal biopsy are required to better determine the relationship between pathological alterations and prognostic characteristics among patients with pamidronate-associated renal impairments.

Clinical features of malignant hypertension with thrombotic microangiopathy.

Thrombocytopenia, microangiopathic hemolytic anemia, and elevated serum lactate dehydrogenase (LDH) clinically characterize thrombotic microangiopathy (TMA), which is frequently recognized among patients with malignant hypertension (MH). Sixteen consecutive patients with MH were retrospectively investigated over a 7-year period and clinical features of the subjects with TMA were evaluated. We confirmed TMA relevant to MH by the normalization of the platelet count and LDH after adequate blood pressure (BP) control was achieved. Thrombotic microangiopathy was found in 7 (44%) of 16 patients. All 7 patients had an elevated plasma renin activity (PRA). Although no significant differences were observed in PRA, the patients with TMA had a significantly higher plasma aldosterone (ALDO) (median: 403 pg/ml; IR: 305 to 568) in comparison to those without TMA (median: 220 pg/ml; IR: 147 to 287; p = 0.013). Overall, ALDO correlated with LDH (r = 0.634, p = 0.0095). However, no significant association was observed between PRA and LDH (r = 0.336, p = 0.2263). The median platelet count nadir of the patients with TMA was 8.4 × 10(4) per µl (IR: 7.15 to 9.95). Thrombocytopenia and elevated LDH were normalized, along with a gradual improvement of BP within an average of 5 days and 21.7 days, respectively. These results suggest that ALDO, but not PRA, may act as a potent indicator of the magnitude of vascular and organ damage related to TMA among patients with malignant hypertension (MH).

A case of cervical cancer-related membranous nephropathy treated with radiation therapy.

Paraneoplastic nephropathy is a rare complication of malignant disease. We present a case of cervical cancer with biopsy-proven membranous nephropathy and associated nephrotic syndrome. Irradiation to the specific neoplasm site and to the metastatic paraaortic lymph node tissues lead to regression of the nephrotic syndrome without causing severe adverse events. Radiation therapy can be the first choice in the treatment of paraneoplastic nephrotic syndrome if the primary neoplasm is unresectable. Invasiveness of intervention and patient prognosis should be carefully deliberated in the management of the two diseases.

The effects of raloxifene on bone turnover markers and bone mineral density in women on maintenance hemodialysis.

BACKGROUND: Bone disease is caused not only by increased bone turnover accompanying secondary hyperparathyroidism but also by factors such as bone metabolic disorder accompanying kidney disease and postmenopausal or age-related osteoporosis in hemodialysis patients. In this study, we investigated the effects of raloxifene on bone turnover markers and bone mineral density (BMD) in female hemodialysis patients to determine involvement of estrogen deficiency in bone disease. METHODS: The subjects were 47 female patients on maintenance hemodialysis. Raloxifene hydrochloride (60 mg) was administered to 21 patients for 1 year, and these patients were compared with a control group of 26 patients. Serum levels of N-terminal cross-linking telopeptide of type I collagen (NTx), bone alkaline phosphatase, and intact parathyroid hormone were measured, and BMD was determined by quantitative heel ultrasound as the speed of sound (SOS) in the calcaneus over this period. RESULTS: NTx decreased after treatment with raloxifene for 1 year, but significantly increased in the control group. SOS increased after treatment with raloxifene for 1 year, but significantly decreased in the control group. Treatment with raloxifene resulted in a significant decrease of NTx and a significant increase of SOS in subgroups of patients aged <60 and ≥ 60 years. CONCLUSIONS: Treatment with raloxifene can suppress a rise in NTx and increase bone mineral density in patients around the time of menopause and in postmenopausal patients of advanced age. A reduction in bone mineral density caused by estrogen deficiency may be involved in the development of bone disease in female hemodialysis patients.

Protein kinase A regulates GDNF/RET-dependent but not GDNF/Ret-independent ureteric bud outgrowth from the Wolffian duct.

Embryonic kidney development begins with the outgrowth of the ureteric bud (UB) from the Wolffian duct (WD) into the adjacent metanephric mesenchyme (MM). Both a GDNF-dependent and GDNF-independent (Maeshima et al., 2007) pathway have been identified. In vivo and in vitro, the GDNF-dependent pathway is inhibited by BMPs, one of the factors invoked to explain the limitation of UB formation in the unbudded regions of the WD surrounding the UB. However, the exact mechanism remains unknown. Here a previously described in vitro system that models UB budding from the WD was utilized to study this process. Because Protein kinase A (PKA) activation has been shown to prevent migration, morphogenesis and tubulogenesis of epithelial cells (Santos et al., 1993), its activity in budded and non-budded portions of the GDNF-induced WD was analyzed. The level of PKA activity was 15-fold higher in the unbudded portions of the WD compared to budded portions, suggesting that PKA activity plays a key role in controlling the site of UB emergence. Using well-characterized PKA agonists and antagonists, we demonstrated that at various levels of the PKA-signaling hierarchy, PKA regulates UB outgrowth from the WD by suppressing budding events. This process appeared to be PKA-2 isoform specific, and mediated by changes in the duct rather than the surrounding mesenchyme. In addition, it was not due to changes in either the sorting of junctional proteins, cell death, or cell proliferation. Furthermore, the suppressive effect of cAMP on budding did not appear to be mediated by spread to adjacent cells via gap junctions. Conversely, antagonism of PKA activity stimulated UB outgrowth from the WD and resulted in both an increase in the number of buds per unit length of WD as well as a larger surface area per bud. Using microarrays, analysis of gene expression in GDNF-treated WDs in which the PKA pathway had been activated revealed a nearly 14-fold decrease in Ret, a receptor for GDNF. A smaller decrease in GFRα1. a co-receptor for GDNF, was also observed. Using Ret-null WDs, we were able to demonstrate that PKA regulated GDNF-dependent budding but not GDNF-independent pathway for WD budding. We also found that BMP2 was higher in unbudded regions of the GDNF-stimulated WD. Treatment of isolated WDs with BMP2 suppressed budding and resulted in a 3-fold increase in PKA activity. The data suggests that the suppression of budding by BMPs and possibly other factors in non-budded zones of the WD may be regulated in part by increased PKA activity, probably partially through downregulation of Ret/GFRα1 coreceptor expression.