Joint disease in haemophilia: Pathophysiology, pain and imaging.

Haemarthroses cause major morbidity in patients with haemophilia. Blood has devastating effects on all joint components, resulting in synovitis, osteochondral degeneration and ultimately end-stage haemophilic arthropathy. Key players in this process are iron and inflammation. Preventing joint bleeds is of utmost importance to maintain joint health as targeted therapies directed against blood-induced inflammation and iron-mediated processes are lacking. Joint bleeds result in acute pain as well as chronic pain due to synovitis or arthropathy. Acute pain originates from nociceptors activated by tissue damage. In chronic inflammation, central and peripheral sensitization of nociceptors might occur resulting in chronic pain. This also triggers a series of brain disorders such as emotional fear, anxiety, mood depression and impairment of cognitive functions. Treatment of haemophilia-related pain not only consists of analgesics, but also of exercise, education and in selected cases antidepressants and anticonvulsants. For objective assessment of joint structural outcome and detecting earlier changes of haemophilic arthropathy, both ultrasound (US) and magnetic resonance (MR) imaging have shown valuable. Both can be considered equally able to reveal signs of disease activity. MR imaging is able to visualize haemosiderin deposition and is more comprehensive in depicting osteochondral changes. Disadvantages of MR imaging are the duration of the examination, evaluation of a single joint at a time, costs and may require sedation, and it may need intraarticular contrast injection to depict initial osteochondral changes with accuracy. As such, US is a more useful screening tool and can be used for repeated follow-up examinations.

Current view and outcome of ITI therapy - A change over time?

INTRODUCTION: Inhibitor development in people with haemophilia is a serious complication that may require intensive and costly interventions. The goal of inhibitor management should be permanent inhibitor eradication through immune tolerance induction (ITI), but well-designed studies are lacking and the management of patients is therefore defined by the experience and views of the clinician. OBJECTIVES: To explore the current clinical practice and outcome of ITI therapy in Europe and how this may have changed over the last decade, as well as to provide consensus recommendations to guide clinicians in their clinical practice. METHODS: A survey was conducted among 16 European haemophilia comprehensive care centres to evaluate current ITI treatment regimens and success rates in severe and mild/moderate haemophilia A and haemophilia B. In addition, an updated literature review was performed as guidance for providing recommendations. RESULTS: We demonstrated successful inhibitor treatment in 86% of severe haemophilia A patients with low responding (LR) and 59% of patients with high responding (HR) inhibitors. Some new trends in the management of patients with inhibitors were identified, including a tendency to use low-dose regimens (<50IU/kg/d) in both children and adults with HR inhibitors possibly based on similar success rates demonstrated in the I-ITI study compared to a high-dose protocol. Data on ITI therapy in mild and moderate haemophilia as well as haemophilia B were limited. CONCLUSIONS: The outcome of ITI therapy seems to be stable over time, and treatment regimens remain heterogeneous. The use of low dose regimens however is considered more frequently.

Expression and release of platelet protein disulphide isomerase in patients with haemophilia A.

INTRODUCTION: Despite similar residual factor VIII activity, patients with haemophilia A (HA) show significant interindividual variability with regard to bleeding frequency and severity, suggesting that additional factors modulate thrombin generation and fibrin deposition. Protein disulphide isomerase (PDI) is an abundant oxidoreductase that exerts pleiotropic effects in primary and secondary haemostasis and contributes to thrombosis and vascular inflammation. AIM: We conducted a pilot study to explore a potential role of platelet PDI in patients with HA. METHODS: Expression and release of platelet PDI were studied by flow cytometry and enzyme-linked immunosorbent assay, respectively. RESULTS: Compared to healthy male controls (n = 12), patients with HA (n = 24) showed significantly increased expression of PDI antigen on ADP- or TRAP-6-, but not on buffer-treated platelets, a finding that could not be explained by enhanced platelet activation, as indicated by expression of the α-granule protein, CD62P (P-selectin). While platelet agonists did not affect PDI secretion in healthy male controls, increased levels of PDI antigen were found in supernatants of TRAP-6-treated platelets from patients with HA. Importantly, in two patients with exceedingly high TRAP-6-induced PDI release over baseline, findings were consistent when platelets were isolated and stimulated on a separate occasion. No obvious association was found between platelet PDI and bleeding phenotype in this patient cohort. CONCLUSION: Agonist-induced expression and release of platelet PDI were increased in patients with HA. Larger studies are needed to clarify if variations in this platelet response contribute to the diversity in bleeding frequency and severity among patients with congenital factor VIII deficiency.

Diagnostic and prognostic value of factor VIII binding antibodies in acquired hemophilia A: data from the GTH-AH 01/2010 study.

UNLABELLED: Essentials Factor VIII (FVIII) binding IgG detected by ELISA could be an alternative to the Bethesda assay. We studied the performance of anti-FVIII IgG ELISA in patients with acquired hemophilia and controls. Anti-FVIII IgG > 99th percentile of controls was highly sensitive and specific. Patients with high anti-FVIII IgG have a lower chance of achieving remission. SUMMARY: Background Acquired hemophilia A is a severe bleeding disorder that requires fast and accurate diagnosis as it occurs often unexpectedly in previously healthy men and women of every age. The Nijmegen-modified Bethesda assay is the diagnostic reference standard for detecting neutralizing autoantibodies against factor VIII (FVIII), but is not widely available, not ideal for quantifying the complex type 2 inhibitors seen in acquired hemophilia, and suffers from high inter-laboratory variability. Objectives To assess the diagnostic and prognostic value of FVIII-binding antibodies as detected by ELISA compared with the Nijmegen Bethesda assay. Methods Samples from the time of first diagnosis and clinical data were available from 102 patients with acquired hemophilia enrolled in the prospective GTH-AH 01/2010 study. Controls (n = 102) were matched for gender and age. Diagnostic cut-offs were determined by receiver-operator curve analysis. The prognostic value was assessed in 92 of the 102 patients by Cox regression analysis of time to partial remission. Results Anti-FVIII IgG above the 99th percentile (> 15 arbitrary units per mL) revealed high sensitivity and specificity (both 0.99; 95% confidence interval, 0.95-1.0) for diagnosing acquired hemophilia. The likelihood of achieving partial remission was related to anti-FVIII IgG concentration (< 300 arbitrary units, 1.0; 300-1050, 0.65; > 1050, 0.39). The Bethesda titer was only associated with the likelihood of partial remission when analyzed in the central laboratory, but not when data from local GTH study sites were used. Conclusion Although the Nijmegen-modified Bethesda assay is the reference standard for demonstrating neutralizing antibodies, the detection of FVIII-binding antibodies by ELISA is similarly sensitive and specific for diagnosing acquired hemophilia. In addition, anti-FVIII IgG may provide prognostic information.

Novel, human cell line-derived recombinant factor VIII (human-cl rhFVIII; Nuwiq® ) in adults with severe haemophilia A: efficacy and safety.

INTRODUCTION: Nuwiq® [human cell line-derived recombinant factor VIII (human-cl rhFVIII)] is a new generation rFVIII protein, without chemical modification or fusion to any other protein, produced in a human cell line. AIM/METHODS: This prospective, open-label, multinational phase III study assessed the efficacy and safety of human-cl rhFVIII in 32 adult previously treated patients (PTPs) with severe haemophilia A during standard prophylaxis for ≥6 months and ≥50 exposure days. Efficacy in treating bleeds and during surgical prophylaxis was also assessed. RESULTS: Prophylactic efficacy, based on mean monthly bleeding rate, was rated as 'excellent' or 'good' in 97% of patients for all bleeds and in 100% of patients for spontaneous bleeds. Mean (SD) annualized bleeding rate was 2.28 (3.73) [median = 0.9] for all bleeds, 1.16 (2.57) [median = 0] for spontaneous bleeds and 1.00 (1.79) [median = 0] for traumatic bleeds. There were no bleeds in 50% of patients and there were no major, life-threatening bleeds. Efficacy was 'excellent' or 'good' in treating 28 (100%) of 28 bleeds. Overall efficacy was rated as 'excellent' during four surgical procedures (three major, one minor) and 'moderate' during one major surgery. Incremental in vivo recovery (IVR) data were comparable with the one-stage and chromogenic assays. IVR was >2.0% per IU kg-1 for all measurements and stable over 6 months. No patients developed FVIII inhibitors and there were no treatment-related serious or severe adverse events. CONCLUSION: These results in adult PTPs indicate that human-cl rhFVIII is effective for the prevention and treatment of bleeds in adults with severe haemophilia A.

The impact of social factors on outcomes in patients with bleeding disorders.

INTRODUCTION: In haemophilia, clinical outcomes are mainly determined by the severity of clotting factor deficiency, treatment regimen, availability of clotting factor concentrate and age. Information about the relevance of patient-related factors such as education, social status or impact of the disease on the patient's life is scarce. AIM: To assess the impact of social status and disease-related impairment of certain aspects of the patient's life on clinical and psychosocial outcomes in patients with inherited bleeding disorders (PWBD). METHODS: Consecutive patients of a single centre were assessed by questionnaires on social status and quality of life (SF-36). Social status was defined by school and professional education, employment and financial income of patients as well as school education of their parents. RESULTS: Fifty-seven PWBD (mean age, 38 ± 16 years) were enrolled, 60% were treated on-demand; PWBD had a median number of 2.5 (0-34) annual bleeds and a median orthopaedic joint score of 6 (0-38). No significant differences were found for clinical and psychosocial outcomes across social status groups. More than half of the patients reported that haemophilia had an impact on their school education, childhood and leisure activities. Patients with a high impact of haemophilia on their lives were less satisfied with their lives (P < 0.002), reported worse quality of life in all domains of the SF-36, had a worse joint score (P < 0.024) and reported more pain (P < 0.013). CONCLUSION: The perceived impact of haemophilia on patients' lives seems to have a stronger impact on clinical and psychosocial outcomes than patients' actual social status.

Successful second ITI with factor IX and combined immunosuppressive therapy. A patient with severe haemophilia B and recurrence of a factor IX inhibitor.

Immune tolerance induction (ITI) in patients with haemophilia B and inhibitors may be complicated by anaphylactic reactions and nephrotic syndrome with lower success rates than in haemophilia A (25% vs. 50-90%). According to case reports, immunosuppressive therapy in addition to high doses of factor IX (FIX) appears to be promising. We report an 18-year-old patient with severe haemophilia B and a FIX inhibitor with a maximum titre of 2.6 Bethesda units and allergic skin reactions to FIX infusions. At 5 years of age, this patient already had a FIX inhibitor with allergic reactions to FIX and activated prothrombin complex concentrate. ITI at 11 years of age with high-dose FIX, dexamethasone, rituximab, mycophenolate mofetil and intravenous immunoglobulins had induced a sustained response until the current presentation. The patient was restarted on the same ITI regimen with aforementioned immunosuppressants, which were initiated one week before high-dose FIX. No allergic reactions, nephrotic syndrome or serious infection occurred during ITI. The FIX inhibitor was undetectable after five weeks of treatment and remained so until 19 months of follow-up.

Relevant bleeding diathesis due to acquired factor XIII deficiency.

BACKGROUND: Acquired factor XIII (FXIII) deficiency is associated with reduced clot firmness and increased bleeding in patients undergoing major surgery. In contrast, only limited information is available on the haemostatic relevance of acquired FXIII deficiency in non-surgical patients. CASE REPORT: An 81-year-old patient, who had experienced acute type-A dissection of the aorta eight years earlier, presented with a 3-year history of progressive mucocutaneous and soft-tissue bleeding. Diagnostic work-up was unremarkable for global coagulation tests, but FXIII and alpha2-antiplasmin were decreased to 33% and 27%, respectively, while plasma D-dimer was elevated to > 35 mg/l. A FXIII inhibitor was excluded by mixing studies. CT scanning revealed a massively elongated and progressively dilated aorta with a false lumen reaching from the left carotid artery to the iliac bifurcation. Bleeding control was achieved by single doses of FXIII at 20-30 IU/kg body weight and tailored oral tranexamic acid. CONCLUSION: Acquired FXIII deficiency with activity levels of 30-35% may confer a severe bleeding tendency in non-surgical patients, especially in the context of increased thrombin an fibrin generation.

Successful eradication of a FVIII inhibitor in a 60-year-old patient with mild haemophilia A using single-agent prednisolone.

BACKGROUND: Development of FVIII inhibitors represents a major challenge in patients with mild haemophilia A (HA), because they tend to occur at an older age and classical immune tolerance induction appears to be less effective. CASE REPORT: A man (age: 60 years) with mild HA due to the missense mutation, Leu1929Arg, received a single dose of rFVIII at 35 IU/kg prior to routine colonoscopy, totalling 25 lifetime exposure days. Two months later, rFVIII was infused for a traumatic hip haematoma. However, FVIII recovery was inappropriate, and a FVIII inhibitor of 19 BU with type-2 kinetics was detected, resulting in FVIII:C of <1%. Two weeks later, the patient experienced spontaneous iliopsoas bleeding. Parallel to bypassing therapy, we started single-agent immunosuppression with prednisolone at 1.5mg/kg. FVIII:C "normalized" at 10.2% after four weeks. After five months, the inhibitor titre fell to <0.4 BU with sustained remission after one year of follow-up. CONCLUSION: In mild HA, FVIII inhibitors may share characteristic features with FVIII autoantibodies commonly observed in acquired HA. Therefore, immunosuppressive therapy alone could be successful at least in a subset of patients.

Pain management in patients with haemophilia: a European survey.

There are no evidence-based guidelines on pain management in people with haemophilia (PWH), who may suffer acute, disabling pain from haemarthroses and chronic arthropathic pain. To review evidence and to investigate current clinical practice in pain assessment and management in PWH the European Haemophilia Therapy Standardisation Board undertook a literature review and a survey in 22 Haemophilia Treatment Centres (HTC), using a questionnaire and seven clinical scenarios. Consensus was sought on pain assessment and management in PWH. Few clinical studies on pain management in PWH were identified. The HTCs care for 1678 children (47% severe haemophilia, 84% on prophylaxis, 17% with arthropathy and 8% with chronic pain) and 5103 adults (44% severe haemophilia, 40% on prophylaxis, 67% with arthropathy and 35% with chronic pain). Analgesics are prescribed by HTCs in 80% of cases (median; range 0-100%) and in 10% (median; range 0-80%) are bought over the counter. Pain and analgesic use are assessed when reported by patients and at check-ups. Only eight centres use a specific pain scale and/or have specific pain guidelines. Two HTCs arrange regular consultations with pain specialists. For acute pain, the preferred first-line drug is paracetamol for children, and paracetamol or non-steroidal anti-inflammatory drugs (NSAIDs) for adults. Children with chronic pain are treated with paracetamol or NSAIDs, whereas adults usually receive Cox-2 inhibitors. Second-line therapy is heterogeneous. There is little published evidence to guide pain assessment and management in PWH, and clinical practice varies considerably across Europe. General and specific recommendations are needed.

Inhibitor-immunology-study. Evaluation of inhibitor development in haemophilia B.

UNLABELLED: The development of inhibitors in haemophilia B is one of the most important complications of replacement therapy, affecting mortality and morbidity. Inhibitor development is based on complex immunological factors, and to date, only little is known about its underlying mechanisms. Here, we present first results of the haemophilia B group of our Inhibitor-Immunology study. PATIENTS, METHODS: So far we have analysed 15 patients with haemophilia B. Four of them developed a high titre inhibitor; the remaining 11 had no inhibitor. We evaluated 9 SNPs in 8 genes (CD40, CTLA-4 , IL-1ß, IL-10, TLR2 , TLR4, TLR9, TNF-α). We compared the distribution of these alleles between inhibitor and non-inhibitor haemophilia B patients and between haemophilia B patients and a normal male control population. HLA typing was performed in all patients. Results, discussion: There appears to be a trend towards a skewed distribution of TLR 9, IL-10 and CTLA4 alleles in haemophilia B patients. Due to the limited number these differences are, however, not statistically significant. The t-test of all patients with inhibitor versus without inhibitor was significant for HLA-A*03 and DPB1*0401 and borderline for DRB1*0201.

Management of acute haemarthrosis in haemophilia A without inhibitors: literature review, European survey and recommendations.

Acute haemarthrosis is a frequent type of bleeding in individuals with haemophilia. Delayed and/or inadequate treatment can trigger a series of pathological changes within the joint, leading to a painful and disabling arthropathy. The early management of intra-articular bleeding has the potential to prevent chronic joint disease and may include a combination of factor replacement, rest, ice, rehabilitation and, in certain cases, joint aspiration. Little data are, however, available regarding the optimal management of acute haemarthrosis, especially with respect to replacement therapy and the use of adjunctive therapies (aspiration, avoidance of weight bearing and immobilization, as well as the use of anti-inflammatory medication and embolization). To provide more insight into the management of acute haemarthrosis in patients with haemophilia, a literature review was conducted. Concomitantly, current management was surveyed in 26 European haemophilia comprehensive care centres representing 15 different countries. The review highlights the need for future robust studies to better define the appropriate replacement therapy and the role of adjunctive therapies such as aspiration. The survey reveals much heterogeneity in the management of acute haemarthrosis across the EU. Within the constraints discussed, treatment recommendations are presented that reflect the literature, current practice and the clinical experience of the European Haemophilia Therapy Standardisation Board (EHTSB).

Inhibitor-Immunology-Study. Different HLA-types seem to be involved in the inhibitor development in haemophilia A.

UNLABELLED: The development of inhibitors is one of the most important complications of replacement therapy in haemophilia, affecting mortality and morbidity. Inhibitor development is based on complex immunological factors. Cytokines and their receptors, T-cell receptors, and the Major Histocompatibility Complex may play important roles in the development of inhibitors. Earlier studies showed non significant associations between HLA class and inhibitor development. Later studies found an increased risk of inhibitor development if there was a combination between certain factor VIII mutations and HLA antigens. We performed HLA typing in 50 patients with haemophilia A in an effort to find associations with inhibitor development. RESULTS: 25 patients had developed an inhibitor (11 low titre, 14 high titre), and 25 never had. In logistic regression analysis, HLA-A 34, DRB1 0405, DRB1 1301 seemed to be involved in inhibitor development and HLA-A 30, B 13, B15, B 57, Cw 12, DQB1 0303, DPB1 0201 protection against inhibitor development. In our patients, the HLA-associations with inhibitor development were different from those in previous publications.

[Haemostatic aspects in clinical oncology]. / Hämostaseologische Aspekte in der Onkologie.

The clinical link between cancer and thrombosis has been recognized by Armand Trousseau in 1865. It has now become clear that clotting activation in malignancy not only plays an important role in the evolution of venous thromboembolism (VTE) or systemic coagulation disorders such as disseminated intravascular coagulation, but that multiple components of the haemostatic and fibrinolytic systems are directly involved in tumour progression. In particular, tissue factor (TF) appears to be involved in several pathways relevant to cancer growth and metastasis. Increasing evidence emerges that haemostatic perturbances in cancer patients are, at least in part, controlled by defined genetic events in molecular tumourigenesis including activating and inactivating mutations of oncogenes and tumour suppressor genes, respectively. Long-term therapy with low-molecular-weight heparin (LMWH) is considered as standard treatment for cancer-associated VTE. However, several experimental studies and clinical trials suggest that LMWH may also be beneficial as an adjunct in the treatment of patients with malignant disease. This article provides an overview on the significance, pathogenesis and treatment of cancer-related clotting disorders as well as on the cellular and molecular mechanisms, by which haemostatic components such as TF, platelets and fibrin(ogen) drive tumour progression.

Dose-dependent effect of etoposide in combination with busulfan plus cyclophosphamide as conditioning for stem cell transplantation in patients with acute myeloid leukemia.

To evaluate the efficacy and toxicity of two different etoposide (VP-16) dosages (30 or 45 mg/kg) in combination with busulfan/cyclophosphamide as conditioning therapy followed by stem cell transplantation in acute myeloid leukemia (AML), 90 patients with AML received either 30 mg/kg (n = 60) or 45 mg/kg (n = 30) etoposide in combination with busulfan (16 mg/kg) and cyclophosphamide (120 mg/kg). The stem cell source was allogeneic related bone marrow (BM) (n = 53), allogeneic unrelated BM (n = 5), allogeneic unrelated peripheral blood (PBSC) (n = 2), syngeneic BM (n = 2), autologous BM purged (n = 9) or unpurged (n = 9), autologous PBSC (n = 10). Fifty-six patients (62%) were in first CR, 26 (29%) were > first CR, and eight (9%) were transplanted in relapse. Principal toxicities in both groups were mucositis and hepatotoxicity. Forty-five mg/kg etoposide resulted in greater hepatic toxicity (P = 0.03), and a higher incidence of VOD (23 vs 12%, P = 0.04) and acute GVHD grade III/IV (13 vs 5%, NS). The treatment-related mortality was 17% in the 30 mg/kg group and 33% in the 45 mg/kg group, mainly due to infections, intestinal pneumonia and GVHD. Hematological recovery of leukocytes 1/nl was comparable in both groups (17 vs 16 days). After a median follow-up of 16 months 19% in the 30 mg/kg group and 23% in the 45 mg/kg group relapsed. In patients who had undergone allogeneic related bone marrow transplantation in first CR no relapses occurred after a median follow-up of 3 years. For all patients the 3-year estimated disease-free survival was 62% in the 30 mg/kg group and 40% in the 45 mg/kg group (P = 0.03). For patients in first CR who underwent allogeneic related stem cell transplantation the 3 year disease-free survivals were 80% and 66%, respectively (P = 0.4). We conclude that etoposide 30 mg/kg or 45 mg/kg in combination with busulfan/cyclophosphamide is a highly active regimen for bone marrow transplantation of patients with AML with a low relapse rate. However, conditioning with 30 mg/kg rather than 45 mg/kg etoposide resulted in less toxicity and a better overall survival due to a lower transplant-related mortality. Bone Marrow Transplantation (2000) 26, 711-716.

The use of dose-intensified chemotherapy in the treatment of metastatic nonseminomatous testicular germ cell tumors. German Testicular Cancer Study Group.

With the use of a cisplatin-based chemotherapy, metastatic testicular cancer has become a model for a highly curable malignant disease. Current data show that 70% to 80% of patients with this disease will achieve long-term survival following cisplatin/etoposide/bleomycin therapy. The role of high-dose chemotherapy with autologous stem cell support is being investigated in metastatic germ cell cancer in attempts to improve outcome for patients whose disease relapses after standard-dose chemotherapy and for those who present initially with advanced metastatic disease. Prognostic categories for patients receiving high-dose salvage chemotherapy have recently been developed: cisplatin-refractory disease, beta-human chorionic gonadotropin values greater than 1,000 U/L, and primary mediastinal germ cell tumors are factors characterizing patients who will derive less benefit from high-dose chemotherapy than those with chemosensitive disease at relapse. While standard-dose salvage chemotherapy achieves only a 20% long-term survival rate, high-dose salvage chemotherapy may yield a cure rate of approximately 40%. A randomized study comparing high-dose therapy with conventional-dose therapy (IT94 coordinated by the European Group for Blood and Marrow Transplantation) in patients with relapsed disease is ongoing to substantiate this observation. The use of dose-intensive therapy as first-line treatment is currently being studied by several institutions. High-dose therapy may be better tolerated when used first line compared with its use in the salvage situation, and may also achieve a rapid initial cell kill before cytostatic drug resistance develops. The German Testicular Cancer Study Group has developed a sequential high-dose combination regimen of cisplatin/etoposide/ifosfamide given with granulocyte colony-stimulating factor and peripheral blood stem cell support for four cycles every 3 weeks. This ongoing study, started in 1990, had accrued 218 patients with advanced testicular germ cell tumors as of June 1997. Of 141 evaluable patients receiving dose levels 1 through 5, 82 (58%) have achieved complete remission with no evidence of disease and 32 (23%) have achieved partial remission with marker normalization. The early death rate was 8%. Overall and event-free survival rates at 2 years are 78% and 73%, respectively, with a projected 5-year overall survival rate of 74%. Despite favorable preliminary results, this approach cannot be considered standard treatment. Currently, high-dose chemotherapy with peripheral blood stem cell transplantation should be administered to patients with testicular cancer only within controlled clinical trials to allow long-term cure rates and treatment-related late side effects to be evaluated.

The relationship between prorenin levels in follicular fluid and follicular atresia in bovine ovaries.

Bovine follicles having a higher concentration of progesterone than estradiol in the follicular fluid can be considered as atretic. Since we observed previously that there was an inverse relationship between the follicular fluid estradiol to progesterone (E/P) ratio and the prorenin level, we have proposed that a high prorenin level may be associated with follicular atresia. The aim of the present study was to corroborate this hypothesis by including additional indices to distinguish unambiguously between atretic and nonatretic follicles and to compare the prorenin levels in these two groups of follicles. The present study included examination of more than 200 follicles in the follicular fluid of which we have measured steroid and prorenin levels. The results obtained show a highly significant negative correlation between the prorenin level on the one hand and the E/P ratio, estrogen to total androgen ratio, or estradiol concentration on the other hand. As a further criterion for atresia, we have examined the histological characteristics of the follicles by light and electron microscopy and have found that 90% of histologically characterized atretic follicles had an E/P ratio less than 1 and an average prorenin level four to five times higher than nonatretic follicles. Finally, when we determined the FSH-stimulated cAMP response and the aromatase activity, in terms of the ability to convert exogenous androgen to estrogen in granulosa cells isolated from individual follicles, we observed a markedly higher prorenin level in the fluid of follicles whose granulosa cells responded poorly to FSH and showed a low aromatase activity, compared to follicles whose granulosa cells responded strongly to FSH and contained high aromatase activity. In summary, follicles that were classified as atretic on the basis of a number of biochemical and histological parameters contained significantly higher prorenin levels in their follicular fluid than nonatretic ones. Thus, a high follicular fluid prorenin level is a valid indicator for follicular atresia in bovine ovaries. However, the reason for this increase in follicular fluid prorenin level and whether this increase is a cause or a consequence of atresia remains to be determined.