Latest Developments in the Management of Nut Allergies

Purpose of review

In this review, we sought to describe the most recent advances in the dietary and medical management of peanut and tree nut allergy, including selective introduction and immunotherapy.

Recent findings

Dietary updates include changes to labeling laws, improved information sources, and new apps for buying foods in shops and overseas to better protect individuals with nut allergies. There are still issues in the management of nut allergies in schools, such as parents having to resort to packed lunches instead of school meals and patients experiencing bullying. Air travel also poses concern, but additional resources are now available to travelers, and recent evidence suggest limited airborne exposure to nuts. The medical management of anaphylaxis is use of epinephrine; however, this remains underutilized. Needle length and administration devices have been recently debated considering the risk of bone penetration vs subcutaneous administration, and autoinjectors seem to deliver higher peak concentrations than syringes. Selective nut introduction has gained momentum in the last 5 years, demonstrating improved quality of life but with the need for motivated parents for continued consumption and available resources for challenges. Immunotherapy to nuts is also a rapidly developing field, with the balance of efficacy and safety being important considerations in the differing modes of administration.

Summary

The management of nut allergies is a rapidly developing field, and dietary and medical management have progressed significantly in the last 5 years. Future research directions include improving safety and efficacy of food immunotherapy and examining patients’ goals for therapy and treatment outcomes.

Economic modelling of diagnostic and treatment pathways in National Institute for Health and Care Excellence clinical guidelines: the Modelling Algorithm Pathways in Guidelines (MAPGuide) project

BACKGROUND

National Institute for Health and Care Excellence (NICE) clinical guidelines (CGs) make recommendations across large, complex care pathways for broad groups of patients. They rely on cost-effectiveness evidence from the literature and from new analyses for selected high-priority topics. An alternative approach would be to build a model of the full care pathway and to use this as a platform to evaluate the cost-effectiveness of multiple topics across the guideline recommendations.

OBJECTIVES

In this project we aimed to test the feasibility of building full guideline models for NICE guidelines and to assess if, and how, such models can be used as a basis for cost-effectiveness analysis (CEA).

DATA SOURCES

A 'best evidence' approach was used to inform the model parameters. Data were drawn from the guideline documentation, advice from clinical experts and rapid literature reviews on selected topics. Where possible we relied on good-quality, recent UK systematic reviews and meta-analyses.

REVIEW METHODS

Two published NICE guidelines were used as case studies: prostate cancer and atrial fibrillation (AF). Discrete event simulation (DES) was used to model the recommended care pathways and to estimate consequent costs and outcomes. For each guideline, researchers not involved in model development collated a shortlist of topics suggested for updating. The modelling teams then attempted to evaluate options related to these topics. Cost-effectiveness results were compared with opinions about the importance of the topics elicited in a survey of stakeholders.

RESULTS

The modelling teams developed simulations of the guideline pathways and disease processes. Development took longer and required more analytical time than anticipated. Estimates of cost-effectiveness were produced for six of the nine prostate cancer topics considered, and for five of eight AF topics. The other topics were not evaluated owing to lack of data or time constraints. The modelled results suggested 'economic priorities' for an update that differed from priorities expressed in the stakeholder survey.

LIMITATIONS

We did not conduct systematic reviews to inform the model parameters, and so the results might not reflect all current evidence. Data limitations and time constraints restricted the number of analyses that we could conduct. We were also unable to obtain feedback from guideline stakeholders about the usefulness of the models within project time scales.

CONCLUSIONS

Discrete event simulation can be used to model full guideline pathways for CEA, although this requires a substantial investment of clinical and analytic time and expertise. For some topics lack of data may limit the potential for modelling. There are also uncertainties over the accessibility and adaptability of full guideline models. However, full guideline modelling offers the potential to strengthen and extend the analytical basis of NICE's CGs. Further work is needed to extend the analysis of our case study models to estimate population-level budget and health impacts. The practical usefulness of our models to guideline developers and users should also be investigated, as should the feasibility and usefulness of whole guideline modelling alongside development of a new CG.

FUNDING

This project was funded by the Medical Research Council and the National Institute for Health Research through the Methodology Research Programme [grant number G0901504] and will be published in full in Health Technology Assessment; Vol. 17, No. 58. See the NIHR Journals Library website for further project information.

S-allylmercaptocysteine, a stable thioallyl compound, induces apoptosis in erythroleukemia cell lines

The antiproliferative potential of S-allylmercaptocysteine (SAMC), a stable organosulfur compound of aged garlic extract, has been investigated using two erythroleukemia cell lines, HEL and OCIM-1. It induces a dose-dependent inhibition of cell growth with a 50% lethal dose of 0.046 mM for OCIM-1 cells and 0.093 mM for HEL cells. [3H]thymidine incorporation was reduced in cells treated with this thioallyl compound, and analysis of high-molecular-weight DNA showed fragmentation compatible with apoptosis. Flow cytometric analyses of DNA revealed an abnormal cell cycle progression in both types of erythroleukemia cells, with the major portion of the unsynchronized cells in the G2/M phase. Measurement of acid-soluble free sulfhydryl groups showed an initial increase in response to SAMC followed by a progressive dose-dependent decrease with extended incubation of cells. We conclude from these studies that SAMC is an effective antiproliferative agent against erythroleukemia cells that induces cell death by apoptosis.

dl-alpha-tocopherol, a potent inhibitor of phorbol ester induced shape change of erythro- and megakaryoblastic leukemia cells

Synthetic vitamin E, dl-alpha-tocopherol, added to a human erythroleukemia HEL and a megakaryoblastic leukemia, Meg-01, cell culture produced potent dose-dependent inhibition of phorbol ester-induced adhesion and of the morphologic changes accompanying it. The inhibition was reversible by withdrawal of supplemental vitamin E from the medium. dl-alpha-Tocopherol also inhibited protein kinase C activity both at baseline and after phorbol ester stimulation. Arachidonic acid stimulated protein kinase C activity of erythroleukemia cells and promoted their adhesion, an effect that was also inhibited by dl-alpha-tocopherol. Introduction of a protein kinase C-neutralizing antibody or a protein kinase C-inhibitor substrate into permeabilized HEL cells inhibited phorbol ester-induced adhesion and shape change. dl-alpha-Tocopherol also affected the cellular distribution of protein kinase C, shifting the major portion of the enzyme to the cytosol fraction and reducing phorbol ester-induced membrane association of the enzyme. Thus, protein kinase C appears to mediate shape change and adhesion, both of which are strongly inhibited by dl-alpha-tocopherol.

Synergism of hemopoietic growth factors on endothelial cell proliferation

Endothelial cells, which are nonhemopoietic cells, express and/or produce most of the known hemopoietic receptors and cytokines. The biological role of these factors, and their respective receptors, on endothelial cells is still unknown. In this study, the authors assessed the effect of different hemopoietic growth factors, ie, interleukin-3 (IL-3), erythropoietin (EPO), macrophage-colony stimulating factor (M-CSF), granulocyte-colony stimulating factor (G-CSF), granulocyte macrophage-colony stimulating factor (GM-CSF), singly or in conjunction with others, on proliferation and chemotaxis of human umbilical vein endothelial cells (HUVECs). They found growth stimulatory activity with IL-3, EPO, and GM-CSF and potent synergism between EPO and IL-3, less with IL-3 and GM-CSF, and none with EPO and either GM-CSF or G-CSF. All the singly tested hemopoietic growth factors stimulated the migration of HUVECs, but in conjunction with other factors, they did not show any additive or synergistic effect.

dl-alpha-tocopherol induces apoptosis in erythroleukemia, prostate, and breast cancer cells

Vitamin E, best known as a potent antioxidant, has been shown to have other functions that are not mediated by this activity. Recent reports have suggested that vitamin E may inhibit smooth muscle cell and also cancer cell growth. We have studied the effect of dl-alpha-tocopherol (vitamin E) on a series of well-established cancer cell lines that included two erythroleukemia cell lines and a hormone-responsive breast and prostate cancer cell line. Cell proliferation was examined in these cell lines, which were maintained at optimal growth conditions. A dose-dependent inhibition of cell growth was found in all cell lines examined, with the MCF-7 breast and CRL-1740 prostate cancer cell lines showing potent suppression of growth at 0.1 mM vitamin E, whereas the erythroleukemia cell lines, HEL and OCIM-1, responded only at > 0.25 mM vitamin E with inhibition of proliferation. Studies of [3H]thymidine incorporation showed that vitamin E supplementation reduced DNA synthesis in all cell lines. Analysis of high-molecular-weight DNA revealed extensive fragmentation, indicating apoptosis of all cell lines supplemented with vitamin E. Our studies thus give evidence of a general inhibition of cell proliferation by dl-alpha-tocopherol, with breast and prostate cancer cells distinctly more sensitive than erythroleukemia cells.

S-allylmercaptocysteine inhibits cell proliferation and reduces the viability of erythroleukemia, breast, and prostate cancer cell lines

Organosulfur compounds are the biologically active components of allium vegetables. Many health benefits have been ascribed to them, including inhibition of carcinogenesis. Inasmuch as several of these thioallyl compounds are quite unstable and others are rapidly inactivated in the body, we have investigated one of the stable components present in aged garlic extract, S-allylmercaptocysteine (SAMC), in an effort to determine whether it can inhibit proliferation of cancer cells. Proliferation and viability of two erythroleukemia cell lines, HEL and OCIM-1, two hormone-responsive breast and prostate cancer cell lines, MCF-7 and CRL-1740, respectively, and normal human umbilical vein endothelial cells in response to different concentrations of SAMC were studied for up to two weeks. There were variations in sensitivity to this organosulfur compound in the different cell lines examined, but the two hormone-responsive cancer cell lines of breast and prostate clearly were far more susceptible to the growth-inhibitory influence of the thioallyl compound. The antiproliferative effect of SAMC was limited to actively growing cells. Human umbilical vein endothelial cells that had reached confluence escaped the reduction in viability so noticeable in the cancer cell lines tested. Our studies thus give evidence of a direct effect of SAMC on established cancer cells.

Erythropoietin receptor mRNA expression in human endothelial cells

A previous report demonstrated that endothelial cells have erythropoietin receptors and respond to this hormone with enhanced proliferation. The present study demonstrates the existence of mRNA for erythropoietin receptor in human umbilical vein endothelial cells. We have reverse transcribed mRNA of endothelial cells and then used different PCR primers to amplify erythropoietin receptor target cDNA between exons 5 and 6 as well as 3-5 in addition to an internal standard DNA fragment. Correspondence of size as well as location of restriction endonuclease scission (Ava II) was used in comparing the amplified fragments of human endothelial cell erythropoietin receptor to those of two human erythroleukemia cell lines, OCIM1 and K562. No alpha- or gamma-globin mRNA was detected in endothelial cells but was readily demonstrable in OCIM1 cells. In addition, to determine whether the expression of human erythropoietin receptor on endothelial cells occurs in vivo, sections of umbilical cord and placenta were immunostained with antibodies against the extracellular portion of the receptor; the results showed strong positive staining of the vascular endothelium.

Erythropoietin has a mitogenic and positive chemotactic effect on endothelial cells

Erythropoietin is known to be a hematopoietic growth factor with a singularly specific action on the proliferation and differentiation of erythroid progenitor cells. We have observed a dose-dependent proliferative action of human recombinant erythropoietin on human umbilical vein endothelial cells and bovine adrenal capillary endothelial cells. Binding studies with radioiodinated recombinant human erythropoietin revealed a large number (approximately 27,000) of an apparent single class of receptors with an affinity in the 10(-9) M range. Linkage of the radiolabeled ligand to its receptor via a bifunctional crosslinking agent allowed us to identify an endothelial cell protein of 45 kDa as the principal receptor associated with this mitogenic effect of erythropoietin. Recombinant human erythropoietin also enhanced the migration of endothelial cells.

Effects of triiodothyronine replacement on the anemia of chronic renal failure

Patients and/or experimental animals with chronic renal failure have decreased serum levels of triiodothyronine (T3), a hormone well known for its erythropoietic activity. The following studies were designed in order to determine whether this observed abnormality in T3 metabolism is an important contributory factor to the etiology of the anemia of uremia. Groups of rats were made chronically uremic by a standard 5/6 nephrectomy technique and received slightly above physiological doses of T3 either by intermittent S.C. injections (twice daily) or by continuous infusion from intraperitoneally implanted osmotic minipumps. After 2 weeks of such treatment, and despite a normalization of serum T3 levels, there were no significant changes in the hematocrit, individual red cell mass, or serum erythropoietin levels of the uremic animals given T3 compared to control rats. We conclude that (1) the decreased serum T3 levels observed in uremia are not an important contributory factor to the pathogenesis of the anemia, and (2) treatment with replacement doses of T3 does not result in significant improvement of erythropoiesis.

Effect of angiotensin infusion on extrarenal erythropoietin production

The effects of infusing subpressor doses of angiotensin II into hypoxic and anemic rats on plasma Ep levels were determined. The effect was greatest when 5 micrograms of angiotensin II per hour was infused into rats made hypoxic 18 hr after nephrectomy. Infusion of larger amounts of angiotensin II had a lesser effect on extrarenal Ep production than did infusion of 5 micrograms/hr. Infusion of angiotensin II into rats nephrectomized 1 hr prior to exposure to hypoxia affected extrarenal Ep production to a lesser degree than the infusion into rats nephrectomized 18 hr prior to hypoxia. In contrast, administration of carbon tetrachloride per os stimulated extrarenal Ep production only when nephrectomy was performed just prior to exposure to hypoxia. Administration of both CCl4 and angiotensin II to hypoxic anephric rats elevated the plasma Ep level to approximately 1.0 IRP U/ml.

Effects of endotoxin on murine erythropoiesis in vitro: role of marrow adherent cells

Endotoxin injected into experimental mice suppresses marrow erythropoiesis by an as yet unknown mechanism. We have studied the effects of endotoxin added to the methylcellulose culture system for growth of erythroid stem cells (BFU-E). The addition of endotoxin decreased BFU-E growth from murine normal (unseparated) femoral marrow mononuclear cells. This suppressive effect was not seen when most of the adherent cells were removed from the culture system prior to the addition of endotoxin. We speculate that whereas "normal" adherent cells provide a favorable microenvironment for the growth of erythroid stem cells, adherent cells altered by endotoxin either loss their ability to support erythroid growth or suppress erythroid colony formation. These observations may be of relevance to the explanation of the pathogenesis of the anemia of infection of chronic diseases.

The effect of estrogens on erythroid stem cells in polycythemic mice

Plethoric mice treated with pharmacological doses of estradiol have decreased concentration of erythropoietin-responsive cells (ERC) in the marrow. We used the methylcellulose-culture system for growth of erythroid stem cells (CFU-E and BFU-E) to define more accurately these estrogen-induced changes. As an animal model we utilized plethoric mice given repeated injections of estradiol cypionate and found that at 14 days after the onset of treatment there was no significant change in the concentration of femoral CFU-E whereas there was a significant decrease of the BFU-E content. Both CFU-E and BFU-E increased progressively in the spleen over a 42-day period. Addition of estradiol directly to the cell-culture system showed no effect on CFU-E growth but induced a significant depression of BFU-E growth. This depression seemed to require the presence of adherent cells. It is our hypothesis that estrogens suppress only the early stages of erythroid proliferation and/or differentiation by a mechanism involving possibly the stromal (adherent) cells of the marrow microenvironment.

Determination of plasma erythropoietin levels: an early marker of tumor activity

A young female patient developed erythrocytosis during the third recurrence of a cerebellar hemangioblastoma. Elevated erythropoietin levels were found in the patient's plasma with normalization after resection of the tumor. High erythropoietin titers were also found in the tumor saline extract. A fourth recurrence of the tumor was heralded by a rising plasma erythropoietin level and gradual erythrocytosis despite the absence of change in the clinical picture or the brain scan. In this case, serial plasma erythropoietin determinations served as a useful early marker of the tumor activity.

Effect of carbon tetrachloride on extrarenal erythropoietin production in rats

Liver regeneration after partial hepatectomy is associated with an increase in extrarenal Ep production; however, this surgical procedure is time-consuming and difficult to standardize. Carbon tetrachloride (CCl4) ingestion in rats is an easy and reproducible way to induce liver damage and regeneration. We therefore studied the effects of CCl4 on extrarenal Ep production in rats. Just as is the case following partial hepatectomy, extrarenal Ep production in response to hypoxia was reduced immediately after ingestion of CCl4. Thereafter it rose to supranormal levels which peaked 3 to 4 days after CCl4 ingestion (at this time Ep titers of nephrectomized, CCl4-fed rats rose to greater than 1.0 U/ml of plasma after exposure to 0.42 atmosphere for 7 hr). Extrarenal Ep production then declined, but was still supranormal 7 days after CCl4. Carbon tetrachloride did not significantly affect extrarenal Ep production in rats nephrectomized 18 hr prior to initiation of hypoxia even if they received injections of renin prior to being made hypoxic, nor did it affect Ep production in response to hypoxia in nonnephrectomized rats under the conditions used in this study.

Effect of protein deprivation on hematopoietic stem cells and on peripheral blood counts

Experiments were performed to determined the effect of protein deprivation on CFU-S in the spleen and femoral marrow, on the peripheral blood counts, and on the rate at which these parameters regenerate following radiation. Splenic CFU-S decrease in number after only 3 days on diets containing 5% protein or less. Marrow CFU-S, on the other hand, decrease only after mice are fed a protein-free diet for 4 weeks or more. The hematocrits, platelet counts, and WBC counts fall in the latter group. Marrow CFU-S regenerate more slowly in irradiated mice fed diets containing 5% protein or less. Also, the hemocrits, WBC counts, and platelet counts of irradiated mice fed diets containing 5% protein regenerate more slowly than do those of irradiated mice fed normal diets. The effect of protein deprivation on erythropoietin production, erythropoiesis, granulocyte function, and immunocompetence is well known. The studies reported here indicate, in addition, that protein deprivation also causes the numbers of CFU-S and the platelet counts to decline.

Effect of protein deprivation on extrarenal erythropoietin production

The production of erythropoietin by rats fed a protein-deficient diet is markedly decreased. This defect can be rapidly reversed by feeding protein. In the reported experiments we investigated the effect of protein deficiency on the extra-renal production of erythropoietin. The results indicate that the production of erythropoietin in nephrectomized animals is insensitive to protein depletion.

Effect of protein deprivation on erythropoiesis

The effects of protein deprivation on erythropoietin (Ep) production were studied. The posthypoxia plasma Ep levels of rats fed a protein-free diet for only 1 day prior to being exposed to 0.5 atmosphere for 7 hr were significantly lower than those of comparably hypoxic rats maintained on a normal diet. The postthypoxia plasma Ep levels were even lower in rats kept on protein-depleted diets for longer periods of time. Rats fed diets with 0.5%, 5% or 12% protein content for 6 days had lower posthypoxia plasma Ep levels than those fed a normal diet (20% protein content). When a single protein meal was force-fed to protein-deprived rats 0-4 hr after initiating the exposure to hypoxia, the posthypoxia plasma Ep levels were significantly higher than in protein-deprived rats that were fed water or dextrose. The posthypoxia plasma Ep titers of protein-deprived rats fed protein 4-8 hr prior to exposure to hypoxia did not differ significantly from those of protein-deprived rats. Although the posthypoxia plasma Ep levels of protein-deprived rats fed a hemolysate containing 0.8 g of hemoglobin 4 hr after beginning hypoxia were greater than those of protein-deprived rats fed only water, the rate of oxygen consumption in these two groups did not differ. We conclude that, in addition to its response to the availability of oxygen, Ep production is infl,enced by the availability of amino acids.

Effect of erythropoietin therapy on the red cell volume of uraemic and non-uraemic rats

Studies were performed to determine the effect of injecting repeated doses of erythropoietin (Ep) on the red cell volume of chronically uraemic rats and on that of non-uraemic sham operated ones. After 13 doses of Ep (5 u/dose), started either 5 or 21 d after removal of five-sixths of the renal mass, the increase in the red cell volume of uraemic rats was as great as that of non-uraemic ones. The significance of these results is discussed.

Effects of partial hepatectomy on extrarenal erythropoietin production in rats

Studies were performed to determine the effects of partial hepatectomy on extra-renal erythropoietin production. Rats were either partially hepatectomized or sham operated. At intervals of from 5 min to 7 days afterward, both kidneys were removed from cohorts of the above two groups of rats and the animals were then exposed to hypoxia for 7.5 hr. Immediately afterward, their plasma was collected and its erythropoietin titer was assayed. Rats which were partially hepatectomized 2-4 days prior to nephrectomy and hypoxia had significantly higher plasma erythropoietin levels than did sham-operated controls, whereas rats hepatectomized 5 min, 1 day, or 7 days prior to nephrectomy and hypoxia did not. These data are consistent with the conclusion that extrarenal erythropoietin production is enhanced in association with rapid regeneration of hepatic cells.

Effect of renin on extrarenal erythropoietin production

Extracts containing renal erythropoietic factor (REF) and others which contain renin reportedly enhance erythropoietin (Ep) titers in the plasma of hypoxic nephrectomized rats. Studies reported here were designed to elucidate the mechanism by which renin increases Ep production in the anephric rat. Injection of a renal extract containing renin significantly raised the blood pressure of anephric rats, and when it was injected just prior to exposure to hypoxia and 15 hour postnephrectomy, the resultant plasma Ep level exceeded that observed in rats exposed to the same hypoxic conditions immediately postnephrectomy. In contrast rats made hypoxic 15 hours after nephrectomy, but not given renin, had plasma Ep levels which were lower than those of anephric rats made hypoxic immediately postoperatively. When renin was injected immediately after nephrectomy or into normal rats, it failed to stimulate Ep production. When diazoxide was injected with the renin extract into hypoxic nephrectomized rats, the vasopressor effect of renin was abolished for 4 hours, and the plasma Ep levels were significantly lower than those of hypoxic nephrectomized animals injected only with renin, Injection of angiotensin II into anephric, hypoxic rats had an effect comparable to that of renin on extrarenal Ep roduction. REF was not detectable in the renin preparation. These results are best explained by the concept that renin and angiotensin increase extrarenal Ep production by causing vasoconstriction and consequently hypoxia in extrarenal sites of Ep production. Also of interest is the finding that plasma EP levels of rats, injected with renin and made hypoxic 15 hours postnephrectomy, are higher than those previously reported to occur in anephric rats.

Mechanism of the increased splenic erythropoiesis in mice treated with estradiol benzoate

Pharmacological doses of estrogens induce osteosclerosis of the bone marrow, and depress colony-forming units (CFU's) and platelet and leukocyte counts in mice. A compensatoryincreasts in mice. A compensatory increase in splenic erythropoiesis prevents a fall in the hematocrit. The mechanism of this compensation was investigated as follows, BDF1 female mice were injected subcutaneously thrice weekly for 6 weeks wiht 50 mugg of estradiol benzoate (EB) or sesame oil (SO). Subsequently the hematocrit, red cell mass (RCM), and 4 hour per cent of 59Fe uptake into the femurs and spleens were determined in groups of five mice for 4 consecutive days. The RCM and hematocrit were not significantly different in the two groups. The per cent of 59Fe uptake into the femurs of EB-treated mice was less than 30 per cent of that in SO-treated mice and the per cent of 59Fe uptake into the spleens of EB mice was more than two times that in SO mice. To ascertain whether the increase in plenic erythropoiesis resulted from an increase in the number of splenic erythropoietin-responsive cells (ERC), the 4 hours per cent 59Fe uptake into the spleen was determined in continuously hypertransfused EB and SO mice injected with erythropoietin (Ep). Whereas hypertransfuction depressed the splenic per cent of 59Fe uptake in EB and SO mice equally, injection of Ep increased the per cent of 59Fe uptake into the spleens of of EB mice to greater than two times that of SO mice. Next, the plasma Ep level of mice injected with EB or SO for 2, 4, or 6 weeks was determined after exposure of the animals to hypoxia. Ep titers were greater than three times higher in EB mice than in SO mice, We conclude that at least two mechanisms act to cause the compensatory increase in splenic erythropoiesis after marrow suppression by EB: (1) the Ep levels rise and (2) the splenic ERC population increases. The latter is probably not due to the increased plasma Ep level because it also occurs in mice whose Ep production is suppressed by plethora.

Factors which affect erythropoiesis in partially nephrectomized and sham-operated rats

Current concepts of the pathogenesis of anemia in uremic animals are derived mainly from the results of studies performed either in vitro or in bilaterally nephrectomized animals. These data may not be applicable to the situation which exists in more chronically uremic animals. In 1932, Chanutin and Ferris showed that removal of five-sixths of the renal mass caused rats to become uremic and to remain so for a prolonged period of time. Rats made uremic in this manner were utilized as models for studying the pathogenesis of the anemia of uremia. Removeal of five-sixths of the renal mass of rats caused their BUNs to rise to over 100 mg/100 ml and to remain at this level for over 3 wk. The hematocrits of these uremic rats fell from 42% to approximately 30% in 3 wk. Erythropoietin (Ep) production immediately fell to a barely detectable level postoperatively and did not increase significantly in 3 wk, although the renal remnant hypertrophied. Extrarenal Ep production also remained at a low level and did not increase during the 3-wk observation period. The response of plethoric uremic rats to 2 units of Ep was as great (in some experiments greater) as that of sham-operated ones. A surprising finding was that plethoric uremic rats, injected with saline rather than with Ep, incorporated more 59Fe into their red blood cells than did sham-operated ones. This finding suggested that in uremic rats erythropoiesis was less markedly suppressed by plethora than it was in non-uremic rats.