Long-term effects of cyclosporin A on cultured mouse pancreatic islets

Fresh and cultured mouse islets differ in their response to nutrient stimulation

Observing different kinetics of nutrient-induced insulin secretion in fresh and cultured islets under the same condition we compared parameters of stimulus secretion coupling in freshly isolated and 22-h-cultured NMRI mouse islets. Stimulation of fresh islets with 30 mM glucose after perifusion without nutrient gave a continuously ascending secretion rate. In 22-h-cultured islets the same protocol produced a brisk first phase followed by a moderately elevated plateau, a pattern regarded to be typical for mouse islets. This was also the response of cultured islets to the nutrient secretagogue alpha-ketoisocaproic acid, whereas the secretion of fresh islets increased similarly fast but remained strongly elevated. The responses of fresh and cultured islets to purely depolarizing stimuli (tolbutamide or KCl), however, were closely similar. Signs of apoptosis and necrosis were rare in both preparations. In cultured islets, the glucose-induced rise of the cytosolic Ca2+ concentration started from a lower value and was larger as was the increase of the ATP/ADP ratio. The prestimulatory level of mitochondrial reducing equivalents, expressed as the NAD(P)H/FAD fluorescence ratio, was lower in cultured islets, but increased more strongly than in fresh islets. When culture conditions were modified by replacing RPMI with Krebs-Ringer medium and FCS with BSA, the amount of released insulin varied widely, but the kinetics always showed a predominant first phase. In conclusion, the secretion kinetics of fresh mouse islets is more responsive to variations of nutrient stimulation than cultured islets. The more uniform kinetics of the latter may be caused by a different use of endogenous metabolites.

Switch to an everolimus-facilitated cyclosporine A sparing immunosuppression improves glycemic control in selected kidney transplant recipients

BACKGROUND

Mammalian target of rapamycin inhibitors (mToRi) allow calcineurin inhibitor (CNI) sparing therapy in renal transplant recipients with possible beneficial effects on the long-term allograft function and cardiovascular risk. The influence of mToRi on glucose metabolism is still under discussion.

METHODS

In a retrospective analysis, renal allograft recipients switched from a cyclosporine A (CsA) to an everolimus (EVR)-based immunosuppression in the first year after transplantation were compared with patients on continued CsA treatment. At 6-month intervals, the prevalence of impaired fasting glucose (IFG) and new onset of diabetes after transplantation (NODAT) were assessed.

RESULTS

A total of 146 renal transplant recipients were included. The cumulative prevalence of IFG and NODAT 30-months post-transplantation was significantly lower in patients switched to an immunosuppression with EVR compared to patients on continued CsA treatment (10% vs 22%, P=.049). However, patients switched to EVR showed a higher incidence of acute cellular rejections in the first 12 months (23% vs 11%, P=.048).

CONCLUSION

EVR-based immunosuppression was associated with a similar or even improved glycemic control and improved renal function. However, due to higher rejection rates, patients switched to EVR should be carefully selected as rejection therapy with steroids counteracts the benefit in glycemic control.

Autologous and Allogenous Antibodies in Lung and Islet Cell Transplantation

The field of organ transplantation has undoubtedly made great strides in recent years. Despite the advances in donor-recipient histocompatibility testing, improvement in transplantation procedures, and development of aggressive immunosuppressive regimens, graft-directed immune responses still pose a major problem to the long-term success of organ transplantation. Elicitation of immune responses detected as antibodies to mismatched donor antigens (alloantibodies) and tissue-restricted self-antigens (autoantibodies) are two major risk factors for the development of graft rejection that ultimately lead to graft failure. In this review, we describe current understanding on genesis and pathogenesis of antibodies in two important clinical scenarios: lung transplantation and transplantation of islet of Langerhans. It is evident that when compared to any other clinical solid organ or cellular transplant, lung and islet transplants are more susceptible to rejection by combination of allo- and autoimmune responses.

Calcineurin inhibitor effects on glucose metabolism and endothelial function following renal transplantation

BACKGROUND

Calcineurin inhibitors (CNI) are involved in the development of post-transplant diabetes mellitus (PTDM). Changes in insulin secretion and sensitivity contribute to the development of PTDM and are associated with endothelial function.

METHODS

In a pre-defined substudy of a previously published randomized trial in renal transplant recipients we compared the effect of CNI treatment (n = 23) with complete CNI-avoidance (n = 21) on insulin secretion and sensitivity (oral glucose tolerance test) as well as endothelial function (laser Doppler flowmetry), 10 wk and 12 months following transplantation.

RESULTS

Insulin sensitivity differed 10 wk post-transplant and was significantly better after 12 months in patients never treated with CNI drugs [0.091 (0.050) vs. 0.083 (0.036) micromol/kg/min/pmol/L, p = 0.043]. Insulin secretion tended to be higher in CNI treated patients at both time points (p = 0.068). Endothelial function was not significantly different at week 10 [540 (205) vs. 227 (565) arbitary units x minutes, p = 0.35] or month 12 [510 (620) vs. 243 (242), p = 0.33].

CONCLUSIONS

Findings in the present study indicate that long-term CNI treatment negatively affects glucose metabolism and this may contribute to the increased risk for premature cardiovascular disease in CNI treated renal transplant recipients. Further studies to elucidate this hypothesis are, however, needed.

Functional and morphological study of cultured pancreatic islets treated with cyclosporine

Cyclosporine A (CsA), a potent immunosuppressive drug, has been found to induce glucose intolerance through its toxic effect on the endocrine pancreas. It is not exactly known whether CsA has a direct effect on the endocrine pancreas or induces its effect indirectly. The present study was therefore undertaken to examine the function and morphology of isolated pancreatic islets when they are directly exposed in vitro to CsA. Pancreatic islets were isolated from adult male Lewis rats using collagenase ductal perfusion technique. The islets were separated with the discontinuous Ficoll gradient technique and further purified by hand picking of the non-islet tissue. The islets were cultured in RPMI-1640, pH 7.4 and maintained at 37 degrees C in a humid atmosphere of 5% (v/v) carbon dioxide in air. Cyclosporine was added to the culture medium to give a final concentration of 1 microg/ml (therapeutic dose), 5 microg/ml (toxic dose), or vehicle (control). Islets were harvested at 1, 4 and 10 days of culture and processed for functional or histological study. The functional study of the islets cultured with 1 microg/ml CsA showed insulin and C-peptide contents similar to those of the control islets. The islets cultured with 5 microg/ml CsA showed a marked decrease in insulin and C-peptide contents. Glucose-dependent insulin release was variable. C-peptide release was lower than that of the control following both the therapeutic and toxic doses of CsA. Phase contrast microscopy showed that the islets cultured with 1 microg/ml CsA were mostly normal looking with a well-defined regular periphery; a few islets had ill-defined or irregular peripheries. The islets cultured with 5 microg/ml CsA had ill-defined irregular peripheries at 1 day, and were dense and forming clumps at 4 and 10 days following culture. There was a decrease in the islet number following the therapeutic dose; the decrease was more following the toxic dose of CsA. The islet diameters increased after the therapeutic dose, but slightly decreased following the toxic dose of CsA. Islets showed a weakly positive immunoperoxidase reaction for insulin that was weaker following the toxic dose of CsA. It is concluded that CsA has a direct effect on B-cells that was proved by the functional and morphological changes seen in the pancreatic islets cultured in vitro.

Impaired insulin response after oral but not intravenous glucose in heart- and liver-transplant recipients

BACKGROUND

The prevalence of diabetes is high after transplantation. We hypothesized that liver transplantation induces additional alterations of glucose homeostasis because of liver denervation.

METHODS

Nondiabetic patients with a heart (n=9) or liver (n=9) transplant and healthy subjects (n=8) were assessed using a two-step hyperglycemic clamp (7.5 and 10 mmol/L). Thereafter, an oral glucose load (0.65 g/kg fat free mass) was administered while glucose was clamped at 10 mmol/L. Glucose appearance from the gut was calculated as the difference between glucose appearance (6,6 2H2 glucose) and exogenous glucose infusion. Plasma insulin, glucagon-like peptide (GLP)-1 and gastric inhibitory polypeptide(GIP) concentrations were compared after intravenous and oral glucose.

RESULTS

After oral glucose, the glucose appearance from the gut was increased 52% and 81% in liver- and heart-transplant recipients (P<0.05). First-pass splanchnic glucose uptake was reduced by 39% in liver-transplant and 64% in heart-transplant patients (P<0.05). After oral but not intravenous glucose, there was an impairment of insulin secretion in both transplant groups relative to the controls. Plasma concentrations of GIP and GLP-1 increased similarly in all three groups after oral glucose.

CONCLUSIONS

First-pass hepatic glucose extraction is decreased after heart and liver transplant. Insulin secretion elicited by oral, but not intravenous glucose, is significantly reduced in both groups of patients. There was no difference between liver- and heart-transplant recipients, indicating that hepatic denervation was not involved. These data suggest an impairment in the beta-cell response to neural factors or incretin hormones secondary to immunosuppressive treatment.

Effect of immunosuppressive doses of cyclosporine on pancreatic beta cell function in pigs

OBJECTIVE

To evaluate whether immunosuppressive doses of cyclosporine (CsA) have an adverse effect on the liver, kidney, and pancreatic beta cells of pigs.

ANIMALS

8 juvenile 8-week-old Landrace X Large White crossbred pigs.

PROCEDURE

CsA (100 to 140 mg/kg) was administered orally to euglycemic pigs to reach whole blood trough concentrations of approximately 1500 ng/mL. To determine pancreatic beta cell function, plasma C-peptide and insulin concentrations were measured in response to i.v. administration of glucose, glucagon, arginine, and oral administration of glucose. Effects on liver and kidney were determined by monitoring serum measurements of liver function and serum creatinine concentrations, respectively.

RESULTS

Plasma concentrations of C-peptide were significantly lower in euglycemic CsA-treated pigs, compared with control pigs, following i.v. administration of glucose, glucagon, arginine, and oral administration of glucose. Furthermore, the glucose clearance rate was decreased in euglycemic CsA-treated pigs, compared with control pigs. Serum creatinine concentrations and 4 of 7 serum measurements of liver function were not adversely affected by CsA administration. Serum concentrations of bilirubin and albumin were significantly increased, and serum alanine aminotransferase activity was significantly decreased in CsA-treated pigs, compared with control pigs. Histologic evaluation of liver and kidney sections revealed no pathologic findings in CsA-treated or control pigs.

CONCLUSIONS AND CLINICAL RELEVANCE

In our study, immunosuppressive doses of CsA caused an impairment of porcine pancreatic beta cell function, but did not have toxic effects on the kidney. However, on the basis of changes in serum bilirubin and albumin concentrations and alanine aminotransferase activity, subclinical toxic effects on the liver did occur when immunosuppressive doses of CsA were administered.

Post-transplant diabetes: incidence, relationship to choice of immunosuppressive drugs, and treatment protocol

Post-transplant diabetes mellitus (PTDM) is one of the feared complications of immunosuppressive therapy. Despite advances, including the introduction of the steroid-sparing calcineurin inhibitors, cyclosporine and tacrolimus, the incidence rate remains greater than 10% to 30%, especially in minority populations. PTDM increases the subsequent risk of both graft loss and patient death, and predisposes patients to all complications of diabetes, including retinopathy and neuropathy. Patients should be monitored closely, especially during the first 3 months post-transplant, and treated aggressively, should glucose intolerance be detected. Minimization of immunosuppression dose, diet, oral hypoglycemic agents, and insulin have all been used in the treatment of PTDM, however, the insulin-sensitizing agents have not been studied. It is hoped that newer immunosuppressive regimens and, ultimately, the ability to achieve tolerance will eventually solve the problem of PTDM.

Regulation of glucose tolerance in patients after liver transplantation: impact of cyclosporin versus tacrolimus therapy

BACKGROUND

We investigated the factors regulating glucose homeostasis in 10 healthy (control) subjects, as well as in stable, long-term, liver-grafted patients receiving monotherapy in the form of either cyclosporin A (n=10) or tacrolimus (n=10).

METHODS

We measured insulin sensitivity, first- and second-phase insulin secretion, with a minimal modeling technique based on the analysis of glucose, insulin, and C-peptide profiles during frequently sampled intravenous glucose tolerance tests (FSIGTT). Proinsulin levels, as a marker of beta-cell dysfunction, were measured in the fasting state and during FSIGTT.

RESULTS

Glucose and insulin concentrations before and after glucose loading did not differ in liver transplant patients and in control subjects. Fasting C-peptide levels in both liver-grafted groups were higher than in healthy subjects and remained elevated during FSIGTT (P<0.05). Intravenous glucose tolerance [(K(G)), i.e. the slope of the regression of logarithm of the blood glucose concentrations vs. time], insulin sensitivity, and first-phase insulin secretion did not differ in liver-grafted groups and healthy subjects. Second-phase insulin secretion was about 56% higher in liver-grafted patients than in controls (P<0.05). Body mass index was the overall determinant of insulin sensitivity in all groups.

CONCLUSIONS

Long-term monotherapy with cyclosporin A or tacrolimus has no deleterious effects on insulin sensitivity, first-phase insulin secretion, and insulin synthesis in liver transplant patients. Normal insulin sensitivity (posthepatic insulin effect) and enhanced second-phase insulin secretion (prehepatic insulin) point to an accelerated hepatic insulin clearance rate in liver transplant patients. Increased hepatic insulin clearance is compensated by enhanced insulin secretion, indicating that insulin clearance is the major determinant of pancreatic function in liver-grafted patients.

Concordant xenotransplantation--non-vascularized pancreatic islets are more difficult to regraft than the vascularized heart

We have previously demonstrated that it is possible to perform retransplantation of a xenogeneic heart (mouse-to-rat) using cyclosporine A as monotherapy, provided that the first heart is transplanted under a short course of deoxyspergualin (DSG). If DSG is omitted, the first heart is rejected within four days and the second heart succumbs to hyperacute rejection within minutes. A mouse heart as first graft does not protect a consecutive pancreatic islet graft, although the heart continues to function after rejection of the cellular graft. One explanation for this discrepancy may be the fact that cellular grafts, as pancreatic islets, lack an endothelial lining. We have, therefore, further investigated possible differences between vascularized and non-vascularized xenografts regarding their capacity to induce unresponsiveness. The use of pancreatic islets as primary graft neither accelerated nor decelerated the speed of rejection of the vascularized heart used as secondary graft. Furthermore, hemagglutinating and cytotoxic antibody titres responded in the same manner as in naive rats transplanted with a mouse heart. Retransplantation with pancreatic islets also resulted in complete rejection of both the primary and secondary grafts. Thus, the lack of unresponsiveness cannot simply be explained by differences, between the pancreatic and cardiac tissues, in antigen expression. In addition, intraperitoneal transplantation of mouse heart cells as primary graft resulted in rejection of a secondary cardiac graft after three days. However, it cannot be totally excluded that the time of antigen exposure had an impact on these results. In conclusion, our previous and present studies suggest that the presence of an intact vascular bed, both in the first and second graft, is necessary to create a state of unresponsiveness. Because the pancreatic islets lack an endothelial lining, they do not benefit from an unresponsiveness of the immune system. Neither are they able to induce such an unresponsiveness.

Cardiovascular effects of an immunosuppressive agent cyclosporin A

Cyclosporin A (CsA) is now routinely used for transplantation of all solid organs, bone marrow transplantation, and for an increasing number of immunological diseases. However, treatment with CsA is an important iatrogenic cause of post-transplant hypertension, hyperlipidemia, and diabetes, which may contribute to the high cardiovascular morbidity in transplant recipients. Recently, the calcineurin inhibitor CsA has been employed in vivo and in vitro to examine the role of calcineurin in the signal transduction leading to cardiac hypertrophy. A cell culture study demonstrated the inhibitory effect of CsA on cytokine production by cardiac myxoma cells, the most common primary tumor of the heart. This review discusses recent data on the cardiovascular effects of CsA.

Implantation of rat insulinoma cell line into cyclosporine treated rats. Effect of the in vivo environment on beta-cell specific gene expression

BACKGROUND

Transplantation of engineered beta cell-derived lines is a promising modality for cell-based therapy of diabetes mellitus. The in vivo environment and antirejection and other medications may have significant effects on the differentiation and proliferation of the transplanted beta cells, thus affecting their function. The effect of the in vivo environment on expression of genes encoding proteins involved in insulin production, secretion, and glucose sensing were analyzed in the RIN 104638 cell line.

METHODS

RIN 104638 cells, were used for s.c. implantation in cyclosporine treated rats and for parallel in vitro culture. The differential expression of the insulin, PDX-1, GLUT-2, and glucokinase genes were assessed by quantitative reverse transcription polymerase chain reaction.

RESULTS

The in vivo environment of cyclosporine-treated rats, preserved most of the differentiated characteristics of the implanted cells. Insulin and glucokinase gene expression were maintained at high levels, although GLUT-2 expression decreased. This was in contrast to the substantial decrease of all the three genes expression when cultured in vitro. Cyclosporine treatment reduced insulin and GLUT-2 gene expression in in vitro culture.

CONCLUSIONS

Beta cell implantation in cyclosporine-treated rats induces alteration in expression of genes pivotal to insulin production and secretion and the glucose sensing abilities. The normal in vivo environment improves the implanted b cell function by increasing the insulin gene expression and content. Furthermore, it reverses some of the dedifferentiating changes caused by the in vitro culture. This may have a positive effect on the therapeutic efficiency of this cell line.

Islet cell damage associated with tacrolimus and cyclosporine: morphological features in pancreas allograft biopsies and clinical correlation

BACKGROUND

The introduction of the potent immunosuppressive drugs tacrolimus (FK) and cyclosporine (CSA) has markedly improved the outcome of solid organ transplantation. However, these drugs can cause posttransplantation diabetes mellitus. Abnormalities in the glucose metabolism are of particular significance in pancreas transplantation.

METHODS

We studied 26 pancreas allograft biopsies, performed 1-8 months posttransplantation, from 20 simultaneous kidney-pancreas transplant recipients, randomized to receive either FK or CSA. The biopsies were studied by light microscopy, immunoperoxidase stains for insulin and glucagon, in situ DNA-end labeling for detection of apoptosis, and electron microscopy. The islet morphology was correlated with the mean and peak levels of CSA and FK in serum, with corticosteroid administration and with glycemia.

RESULTS

On light microscopy cytoplasmic swelling, vacuolization, apoptosis, and abnormal immunostaining for insulin were seen in biopsies from patients receiving either FK or CSA. The islet cell damage was more frequent and severe in the group receiving FK than in the group receiving CSA (10/13 and 5/13, respectively) but the differences were not statistically significant. Significant correlation was seen between the presence of islet cell damage and serum levels of CSA or FK during the 15 days previous to the biopsy, as well as with the peak level of FK. Toxic levels of CSA or FK and administration of pulse steroids were associated with hyperglycemia when these occurred concurrently (P=0.005). Toxic levels of CSA or FK by themselves were associated with hyperglycemia in a minority of cases (8 and 26%, respectively). Electron microscopy showed cytoplasmic swelling and vacuolization, and marked decrease or absence of dense-core secretory granules in beta cells; the changes were more pronounced in patients on FK. Serial biopsies from two hyperglycemic patients receiving FK and evidence of islet cell damage demonstrated reversibility of the damage when FK was discontinued.

CONCLUSIONS

The structural damage to beta cells demonstrated in this study is similar to morphological and functional abnormalities previously described in experimental animal models and can at least partially account for the glucose metabolism abnormalities seen in patients receiving these drugs. Toxic levels of CSA or FK and higher steroid doses potentiate each others' diabetogenic effects.

Risk for posttransplant Diabetes mellitus with current immunosuppressive medications

With improvements in the practice of transplantation and the introduction of new immunosuppressive medications, there has been a substantial increase in 1-year allograft survival rates. Consequently, the pool of potential candidates for organ transplants continues to grow and a greater preponderance of older patients with more comorbidities are undergoing transplantation. As a result, there is interest in such medical complications as posttransplantation diabetes mellitus (PTDM) that develop after the transplantation of a successful allograft. PTDM is an undesirable consequence of transplantation because of its associated morbidity and impairment of both patient and graft survival. Although some controversy exists, it is likely that glucose intolerance after transplantation results in both macrovascular and microvascular disease, and there is an increasing risk for infectious and cardiovascular diseases, to which transplant recipients are already at increased susceptibility. Both experimental and clinical observations have shown that immunosuppressive agents currently used in transplantation account for a large degree of the increased risk for PTDM. Consequently, improved understanding of the effects of currently used immunosuppressive medicines on glycemic tolerance is of interest in clinical transplantation.

Clinical islet cell transplantation. Are we there yet?

Diabetes mellitus is perhaps the most devastating chronic disease of all time. A brief history of the evolution of treatment modalities is provided, culminating in the rationale for the physiologic replacement of a functioning beta-cell mass by transplantation. Vascularized pancreas transplantation is discussed briefly as an introduction to the transplantation of the isolated islet. A detailed review of the current state of human islet transplantation for the cure of diabetes is then described. Finally, areas for future development are highlighted.

Transplantation for the treatment of diabetes mellitus

Pancreas and pancreatic islet cell transplantation have been investigated as potential methods of treatment for diabetes mellitus in both man and animals. Successful transplantation could ultimately provide a cure for insulin-dependent diabetes mellitus. Not only would it greatly improve the quality of life of the diabetic patient, but also prevent the multitude of potential complications of poor glycemic control. Whole pancreas transplantation has been successful as a means of treating diabetes mellitus, however, complications make this treatment less than ideal. The focus of diabetes research in many centers worldwide has been on successful transplantation of the purified endocrine portion of the pancreas. Despite the many years of dedicated research, there remain several important obstacles to successful islet cell transplantation in both human and veterinary medicine. Currently progress is being made to make islet cell transplantation a reality.

Post-transplant diabetes mellitus. The role of immunosuppression

Immunosuppressive agents increase the risk of death due to coronary disease or stroke by their ability to cause 3 different adverse effects: dyslipidaemia, hypertension and hyperglycaemia. Post-transplant diabetes mellitus has emerged as a major adverse effect of immunosuppressants. As recipients of organ transplants survive longer, the secondary complications of diabetes mellitus have assumed greater importance. There is a need for a precise definition of post-transplant diabetes mellitus to facilitate inter-centre comparison and to study the natural history of post-transplant diabetes mellitus. We recommend broad criteria to define hyperglycaemia, as a fasting blood glucose level of > 400 mg/dl at any point or > 200 mg/dl for 2 weeks, or a need for insulin treatment for at least 2 weeks. We also recommend serial measurements of HbA1c. Cyclosporin and tacrolimus cause post-transplant diabetes mellitus by a number of mechanisms, including decreased insulin secretion, increased insulin resistance or a direct toxic effect on the beta cell. For corticosteroids, the induction of insulin resistance seems to be the predominant factor. However, few studies have examined the mechanism of diabetogenicity at the molecular level. This may hold the key for pharmacological manipulation of current immunosuppressive regimens which may result in decreased metabolic complications. Corticosteroid sparing regimens have been shown to reduce the metabolic complications of immunosuppressants including post-transplant diabetes mellitus. However, their use should be balanced against the increased incidence of transplant rejections. Post-transplant diabetes mellitus may be organ-specific irrespective of the immunosuppressant used. Tacrolimus causes a high incidence of post-transplant diabetes mellitus in recipients of kidney transplants (upto 20% in some reports); the diabetogenicity of cyclosporin-based regimens is comparable with that of tacrolimus-based regimens in recipients of liver transplants. A few clinical studies in which attempts were made to discontinue cyclosporin resulted in an unacceptable loss of the transplant. In the case of tacrolimus, complete withdrawal of immunosuppression may be possible in selected patients with liver transplants. However, post-transplant recipients who may benefit from this approach are difficult to identify. In some early series, patients received doses of tacrolimus that were approximately 2 to 3 times higher than those currently used, which may have resulted in a higher incidence of post-transplant diabetes mellitus. More recently, it has been shown that tacrolimus was successful in salvaging whole pancreatic grafts which were maintained on cyclosporin. Tacrolimus-based immunosuppression as primary therapy was also used with remarkable success in solitary whole pancreas transplants. Strategies to reduce the metabolic complications of immunosuppressants should be pursued aggressively as this will directly lead to a decrease in long term cardiovascular adverse effects.

Toxicity in vivo of different immunosuppressive drugs in fetal porcine pancreatic islets

Clinical transplantation of fetal porcine islet-like cell clusters (ICC) to kidney transplanted diabetic patients has shown both morphological and biochemical evidence of prolonged xenograft survival, but no effect was seen on the insulin requirement of the transplanted patients. One possible explanation for this relative lack of success might have been the influence of the immunosuppressive drugs on the differentiation of ICC grafts. In this study, the effects of a number of immunosuppressive drugs on ICC differentiation were investigated. Normoglycemic C57BL/6 nu/nu mice were transplanted with 2x3 microliter ICC under the renal capsule. During a four-week period the animals were treated daily with azathioprine (2.0 mg/kg b.wt.), prednisolone (0.5 mg/kg b.wt.), cyclosporine (5.0 mg/kg b.wt.), cyclophosphamide (5.0 mg/kg b.wt.) 15-deoxyspergualin (5.0 mg/kg b.wt.), leflunomide (30 mg/kg b.wt.) or saline. In order to estimate rates of beta-cell DNA synthesis in the ICC grafts the mice were injected with 3H-thymidine one hour before killing and slides of the grafts were evaluated with regard to autoradiographical labeling. Other ICC grafts were evaluated by measurement of their insulin and DNA contents. Both the DNA content of ICC grafts and the beta cell labeling index in the cyclosporine animals were significantly decreased. Perfusion experiments with graft-bearing kidneys of cyclosporine-treated animals showed a significantly decreased insulin secretion in response to glucose plus theophylline. None of the other drugs influenced the differentiation of grafted ICC as evaluated in this study. Thus, it is obvious that cyclosporine inhibits both the growth and functional differentiation of transplanted ICC, which might be one reason for the relative lack of success in the clinical transplantation of porcine ICC to diabetic patients.

Effect of cyclosporin treatment on metabolic and hormonal responses to mixed meal plus oral glucose in dogs with intrasplenic pancreatic islet autograft

We evaluated the effect of immunosuppressive concentrations of cyclosporin A (CsA), given intramuscularly, on the levels of glucose, insulin, C-peptide, glucagon, pancreatic polypeptide (PP), lactate, alanine and beta-hydroxy-butyrate in a group of pancreatectomized mongrel dogs with intrasplenic islet autografts, given mixed meal and oral glucose, while on or off CsA therapy. In whole blood, HPLC-measured drug levels ranged from 412 to 803 ng/ml. Basal glucose and insulin concentrations did not differ significantly between non-pancreatectomized, control dogs and transplanted animals, whether on or off CsA. After the meal challenge, glucose levels were significantly higher in transplanted animals than in normal dogs, and no additional deleterious effect of CsA was observed. Similar insulin and C-peptide responses were found in animals either on or off CsA treatment. Fasting and post-meal concentrations of glucagon, PP and intermediate metabolites were not affected by the drug. These results suggest that intramuscular CsA, given at doses known to sustain islet allograft function, has no detrimental effect on the hormonal and metabolic responses to mixed meal and oral glucose in dogs with intrasplenic islet autografts.

Acute effects of different immunosuppressive drugs on pancreatic, islet, renal, and arterial hepatic blood flow in anesthetized rats

The effects of four different immunosuppressive drugs on organ blood flow were investigated. Sprague-Dawley rats were injected intravenously with 0.2 ml of either 15-deoxyspergualin (DSG; 5 mg/kg body weight), RS 61443 (80 mg/kg body weight), FK 506 (0.5 mg/kg body weight), cyclosporin A (9.5 mg/kg body weight), or the vehicles used. At 15 or 60 min after injection of the drugs, the blood perfusion of the whole pancreas, the pancreatic islets, and the kidneys, as well as the arterial blood flow to the liver, were measured in anesthetized animals using a microsphere technique. Fifteen minutes after administration, both FK 506 and DSG decreased the fraction of whole pancreatic blood flow diverted through the islets. FK 506 and cyclosporin A reduced renal blood flow, but only 60 min after injection of the drug. None of the drugs influenced hepatic blood flow. RS 61443 did not affect the blood flow of the organ systems investigated. These differences in the effects of the drugs tested on blood flow might have some important implications on their efficacy and side effects. Thus, in view of its lack of influence on organ blood flow, RS 61443 seems to be preferable, at least when compared with cyclosporin A and FK 506 in the context of organ transplantation.

Transplanted beta cell response to increased metabolic demand. Changes in beta cell replication and mass

We determined the capacity of transplanted beta cells to modify their replication and mass when stimulated by changes in metabolic demand. Five groups of Lewis rats were studied: group 1 (Tx-Px) had a 95% pancreatectomy 14 d after transplantation of 500 islets; group 2 (Px-Tx) had a 95% pancreatectomy 14 d before transplantation of 500 islets; group 3 (Tx) was transplanted with 500 islets; group 4 (Px) had a 95% pancreatectomy; and group 5 (normal) was neither transplanted nor pancreatectomized. Blood glucose was normal in Tx-Px and Tx groups at all times. Px-Tx and Px groups developed severe hyperglycemia after pancreatectomy that was corrected in Px-Tx group in 83% of rats 28 d after transplantation. Replication of transplanted beta cells increased in Tx-Px (1.15 +/- 0.12%) and Px-Tx (0.85 +/- 0.12%) groups, but not in Tx group (0.64 +/- 0.07%) compared with normal pancreatic beta cells (0.38 +/- 0.05%) (P < 0.001). Mean beta cell size increased in Tx-Px (311 +/- 14 microns2) and Px-Tx (328 +/- 13 microns2) groups compared with Tx (252 +/- 12 microns2) and normal (239 +/- 9 microns2) groups (P < 0.001). Transplanted beta cell mass increased in Tx-Px (1.87 +/- 0.51 mg) and Px-Tx (1.55 +/- 0.21 mg) groups compared with Tx group (0.78 +/- 0.17 mg) (P < 0.05). In summary, changes in transplanted beta cells prevented the development of hyperglycemia in Tx-Px rats. Transplanted beta cells responded to increased metabolic demand increasing their beta cell mass.

Inhibitory effects of cyclosporin A on rat insulinoma cell proliferation, polyamine content and insulin secretion

The effects of the immunosuppressive drug cyclosporin A on the growth and secretion of clonal rat insulinoma cells (RINm5F) was investigated in vitro. Particular attention was paid to the influence of cyclosporin A on the metabolism of polyamines, since these compounds have been implicated in regulation of the growth and function of insulin-producing cells. It was found that culture of the cells for 2 days in the presence of 0.1 mg/l of cyclosporin A failed to affect RINm5F cell proliferation, polyamine content, cellular insulin content or secretion of insulin into the culture medium. When the concentration of cyclosporin A was raised to 1 mg/l, however, the growth rate and polyamine content of the cells were impeded in parallel with a decreased cellular insulin content and insulin secretion. Replenishment of the intracellular polyamine content by addition of exogenous putrescine failed to prevent the decreased growth rate and insulin content, indicating that cyclosporin A does not exert its inhibitory effect on the growth and insulin content of the RINm5F primarily by decreasing the polyamine content of these cells. Hence, cyclosporin A may be useful in decreasing the rapid growth of insulin-producing tumor cells, but also impairs insulin secretion.

15-Deoxyspergualin prolongs pancreatic islet allo- and xenograft survival in mice

The new immunosuppressant 15-deoxyspergualin was evaluated in allogeneic and xenogeneic pancreatic islet transplantation. In the allograft study 500 collagenase-isolated C57BL/6 mouse islets were transplanted under the renal capsule of alloxan-diabetic C57BL/Ks mice that were either 15-deoxyspergualin-treated (n = 15) or given saline only (n = 8). When 15-deoxyspergualin was given (5 mg/kg b.wt. intraperitoneally) until day 28 after transplantation in a special dosage schedule, 10 out of 15 animals were normoglycaemic one week after transplantation and 6 were still normoglycaemic after ten weeks. All 8 control animals were hyperglycaemic after 18 days. Light microscopy showed graft rejection in hyperglycaemic mice, but only mild infiltration of lymphocytes in the grafts of normoglycaemic animals. In the xenograft study C57BL/Ks mice were transplanted under the renal capsule with 500-750 foetal porcine islet-like cell clusters. The grafts were examined for evidence of rejection with light microscopy at different time points after implantation. In the control animals given saline only (n = 37) there was progressive evidence of rejection starting on day seven. In 15-deoxyspergualin treated animals (2.5 mg/kg intraperitoneally; n = 27) there was significantly less infiltration at days 7, 14 and 21. After 32 days there was, however, no difference between controls and 15-deoxyspergualin treated mice. A doubling of the 15-deoxyspergualin dose (5.0 mg/kg intraperitoneally; n = 5) did not further improve the survival of the xenografted islet-like cell clusters. There was no synergistic effect when cyclosporine A (12.5 mg/kg intraperitoneally) was added to the 15-deoxyspergualin therapy (n = 34).(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of cyclosporin A on the blood flow of the native and transplanted rat pancreas and duodenum

The aim of the present study was to evaluate the effects of cyclosporin A (CyA) on the blood perfusion of the transplanted pancreas. For this purpose syngeneic pancreaticoduodenal transplantations were performed in Wistar-Furth rats. After nephrectomy the graft was anastomosed using a nonsuturing cuff technique to the left renal vessels. Beginning 7 days after transplantation and then continuing for 2 weeks, CyA (15 mg/kg body weight) or vehicle was given p.o. once daily, 6 days a week. The serum CyA concentrations were greater than 600 ng/ml at all points in time tested. Intraperitoneal glucose tolerance tests were normal in CyA-treated animals after 12 days, but the pancreatic insulin concentration was decreased to the same extent in the native and transplanted pancreas. A microsphere technique was used to measure the blood perfusion of the pancreaticoduodenal graft, the native pancreas and duodenum, and remaining kidney 14 days after starting the CyA treatment. The renal blood flow was markedly decreased by CyA when compared with the control animals. In rats given vehicle alone, pancreatic, islet, and duodenal blood flows were higher in the graft than in the corresponding native organs. However, in rats given CyA, hyperperfusion of the graft was not observed. We conclude that the administration of CyA prevents the transplantation-induced blood flow increase seen in pancreaticoduodenal grafts of vehicle-treated rats. These observations may reflect graft denervation.

Effects of the immunosuppressants cyclosporin A and FK 506 on exocytosis in the rat exocrine pancreas in vitro

1. We have examined the effects of the immunosuppressive drugs cyclosporin A (CsA) and FK 506 on exocytosis in two in vitro preparations of the exocrine pancreas-lobules and dispersed acini. 2. In lobules taken from starved rats and stimulated with the secretagogue caerulein, both CsA and FK 506, given shortly before stimulation, caused a dose-dependent inhibition of amylase secretion. In lobules from rats that had been pretreated in vivo with the protease inhibitor FOY-305 to stimulate secretion maximally, both CsA and FK 506 inhibited secretion of newly synthesized proteins, whereas only FK 506 inhibited caerulein-stimulated amylase release. 3. These different effects of the immunosuppressants on amylase release were reflected in their effects on degranulation, as revealed by electron microscopy. Control acinar cells in lobules from FOY-305-treated rats were almost completely degranulated, whereas treatment with FK 506, but not CsA, caused the accumulation of zymogen granules close to the apical plasma membrane. 4. In dispersed acini, stimulated with the cholinomimetic secretagogue bethanechol, both CsA and FK 506 reduced the secretory response, to about 45% of control; IC50 values were 50 nM and 3 nM, respectively. A similar partial inhibition of exocytosis was seen in acini permeabilized with the bacterial toxin streptolysin O and stimulated with 10 microM Ca2+. 5. These results demonstrate that the immunosuppressants cause an inhibition of exocytosis in the exocrine pancreas that is both rapid in onset and potent. The loss of the inhibitory effect of CsA on amylase release in lobules taken from FOY-305-treated rats may reveal a change in the characteristics of exocytosis as a consequence of the high level of stimulation, and also indicates that CsA and FK 506 have subtly different effects on secretion. We suggest that these drugs might be useful tools in the dissection of the molecular mechanisms of exocytosis.

Beta cell mass and growth after syngeneic islet cell transplantation in normal and streptozocin diabetic C57BL/6 mice

In islet transplantation, nonimmunological factors such as limited growth capacity or increased death rate could reduce the beta cell mass in the graft and lead to failure of the transplant. We studied the evolution of beta cell replication and mass after transplantation of insufficient, minimally sufficient, or excessive islet tissue. Streptozocin diabetic C57BL/6 mice received 150 or 300 syngeneic islets under the kidney capsule and normal mice received 300 islets. In streptozocin diabetic mice 300 islets restored normoglycemia; beta cell replication in transplanted islets was similar to replication in normal pancreas and beta cell mass in the graft remained constant. In contrast, 150 islets were insufficient to achieve normoglycemia; beta cell replication was increased initially but not by 18 or 30 d despite persistent hyperglycemia, and beta cell mass fell progressively. When islets were transplanted into normal recipients, beta cell replication remained normal but beta cells underwent atrophy and mass in the graft was substantially reduced. Therefore, with a successful islet transplant, in diabetic mice beta cell replication and mass remain constant. In contrast, when insufficient islet tissue is transplanted an initial increase in beta cell replication can not compensate for a decline in beta cell mass. When excessive islet tissue is transplanted, beta cell mass is reduced despite normal beta cell replication.

In vivo and in vitro effects of cyclosporin A on glucose transport by soleus muscles of mice

The effect of cyclosporin A (CyA) on 2-deoxyglucose (2DG) uptake by soleus muscles of ICR mice was studied in vivo and in vitro. The basal and insulin-stimulated uptakes of 2DG by the muscles as well as the plasma insulin level were significantly decreased by the in vivo treatment of mice with 20 mg/kg/day of CyA for 6 weeks (P less than 0.01 and P less than 0.05), whereas the insulin binding was increased inversely in the muscles from 20 mg/kg/day CyA-treated mice. The insulin-stimulated uptake of 2DG by the muscles was significantly decreased by the in vitro treatment of the muscles with 1, 10 and 100 micrograms/mL of CyA (P less than 0.05 and P less than 0.01, respectively), while the basal uptake of 2DG was not changed by the in vitro treatment of the muscles with CyA. The insulin binding to the muscles was not altered by the in vitro treatment of the muscles with CyA. These findings suggest that CyA affects not only the insulin secretion from the pancreatic islets but also the postbinding mechanisms of insulin action on the glucose transport by the muscles, which may account for a part of the diabetogenic effect of CyA.

Alteration of pancreatic B-cells in Wistar rats treated with non-diabetogenic doses of cyclosporin A

We have investigated the effect of non-immunosuppressive cyclosporin A (CS-A) doses on glucose tolerance, pancreatic insulin content, insulin content of isolated islets and insulin secretion in vitro in response to glucose. Within 12 weeks animals treated permanently with a dose of 2.5 mg CS-A/kg b.wt. developed glucose intolerance (but not hyperglycaemia) accompanied by a decrease of pancreatic insulin content due to a decrease of islet insulin content, whereas the relative B-cell volume density was not changed. Isolated islets obtained from rats treated for 4 weeks had a diminished sensitivity for glucose, whereas islets obtained from animals treated for greater than 4 weeks showed a diminished half-maximum and maximum secretion rate. Rats treated for 12 weeks with 1.25 mg CS-A/kg b.wt. developed an impaired glucose tolerance after 8 weeks accompanied by a diminished pancreatic insulin content. Despite continued treatment the pancreatic insulin content was able to increase and the glucose tolerance to normalize, indicating an adaptation of pancreatic B-cells to CS-A. The results support the theory that a potential toxic effect of cyclosporin A can be diagnosed by functional tests (e.g. insulin secretion in response to a stepwise increase of glucose) before the irreversible (e.g. morphological) alterations occur.

Allotransplantation of canine pancreatic islets

The complications of diabetes continue to present significant health risks despite improvements in conventional insulin therapy. Transplantation of pancreatic islet tissue has the potential to provide more precise glucose regulation and possibly minimize these implications. Recent advances in pancreatic islet isolation technology have facilitated investigation of islet allograft function in large animal models. These studies are fundamental to the development of methods for transplantation of allogeneic or xenogeneic islets in diabetic patients. This paper reviews the approaches which have been taken to prevent rejection and allow assessment of islet allograft function in the pancreatectomized dog model. These approaches include immunosuppression, immunomodulation of the donor tissue and isolation of allogeneic tissue within an immunoprotective membrane.

The pathophysiology of Sandimmune (cyclosporine) in man and animals

Part II: The side-effects of Sandimmune that have also been observed clinically include hepatic dysfunction, glucose intolerance, thrombo-embolic complications and nervous system disorders. To determine the cause and significance of such effects, the actions of Sandimmune on the liver, the pancreas, on hematostasis and the nervous system were examined. Comparisons were made between animal and human data obtained in vivo and in vitro, and the clinical setting under which the side-effects occur was analyzed. The actions of Sandimmune on the liver seem to reflect mostly a cholestasis with a small depression in protein synthesis and a mild disturbance in lipid metabolism of uncertain origin. The action of Sandimmune on the pancreas suggests insulin resistance and possibly a secretory disturbance, with no evidence for depressed insulin synthesis, except in animals at high doses. Sandimmune does not seem to promote thromboembolism in man, although fibrinolysis may be depressed and platelet aggregation can be enhanced. The effects of Sandimmune on the nervous system are unclear, for tremor is common but of uncertain origin, whereas seizures and encephalopathy are rare and invariably associated with other risk factors.

Histological and ultrastructural effects of cyclosporin A on normal human skin xenografted on to nude mice

Cyclosporin A (CsA) is a potent immunosuppressant with a selective activity on T-helper lymphocytes. However, CsA also exerts biological effects on non-lymphoid cells (fibroblasts, endothelial and epithelial cells). CsA can inhibit in vivo and in vitro DNA synthesis of epidermal keratinocytes (EK) and induces in vivo morphological alterations of kidney epithelial cells. In the present study we investigated the in vivo effects of a short-term CsA treatment (50 mg/kg per day) on DNA synthesis (evaluated through 5-bromo-2'-deoxyuridine incorporation) and on the histological features of normal human skin xenografted (NHSX) on to congenitally athymic nude mice. When compared with control NHSX, CsA induced a statistically significant inhibition of DNA synthesis of NHSX EK. At the light- and electron-microscopic level, apart from a decrease in the thickness of the viable epidermis of NHSX (statistically non-significant), no noticeable differences between treated and control NHSX could be detected. EK, Langerhans cells and melanocytes appeared morphologically unaffected by CsA and no signs of acute toxicity (giant mitochondria, vacuolization, microcalcifications) were seen. These results suggest that CsA exerts a subtle effect on human EK; indeed, despite an unequivocal antiproliferative activity, no significant histological changes related to the acute CsA toxicity seem to be induced on the various epidermal cell types.

Cyclosporin A exerts a cytostatic effect in vivo on human and murine epithelial cells

Cyclosporin A (CsA) is a potent immunosuppressant that may also affect nonlymphoid cells. Indeed, CsA exerts a growth inhibition in vitro of several human and animal, normal and neoplastic cell types. To assess a possible in vivo direct cytostatic activity of CsA, the authors evaluated the proportion of S-phase (5-bromo-2'-deoxyuridine incorporating) cells of epithelial origin (skin, tongue, esophagus) of congenitally athymic (nude) mice bearing xenografts of human skin and receiving a daily subcutaneous injection of 50 mg/kg of CsA for 3 weeks. As compared with control animals, CsA-treated mice showed a decreased labeling index (LI) of all the epithelial tissues studied, which was statistically significant in the case of epidermis (both human and murine) and the tongue. Because nude mice lack T-cell-mediated immunity, these results suggest that CsA also exerts an immunologically independent antiproliferative activity on epithelial cells in vivo and they also highlight the interest in pursuing studies on cyclosporins as cytostatic agents.

Adverse effects of cyclosporine on islet growth and differentiation

In light of recent evidence that cyclosporine (CsA) inhibits growth of the exocrine pancreas, we decided to examine the effects of cyclosporine in a hamster model of islet cell proliferation and differentiation induced by partial pancreatic duct obstruction (PPDO), in which the growth of pancreatic endocrine tissue is mediated by production of an islet cell growth factor (ICGF) contained in a cytosolic extract of pancreas. In Part I of this study, extract was prepared from PPDO pancreas, from PPDO pancreas in animals treated with CsA (20 mg/kg ip daily for 10 days), and from pancreas in control animals. Data obtained from an in vivo bioassay confirmed that administration of the extract derived from PPDO and PPDO + CsA animals increased pancreatic organ weight significantly by 10 and 17%, respectively, compared to control. Similarly, total pancreatic DNA content was increased significantly by 25 and 41%, respectively. In Part II of the study, the direct effect of CsA on islet cell proliferation and differentiation induced by PPDO was examined. The number of islets per square millimeter and the uptake of tritiated thymidine by islet cells (%) were increased significantly in PPDO animals (2.4 +/- 0.1 and 0.56 +/- 0.06) compared to those in PPDO + CsA animals (1.2 +/- 0.1 and 0.24 +/- 0.01) and to those in controls (1.1 +/- 0.0 and 0.22 +/- 0.07). It is concluded from the data in Part I that CsA does not inhibit ICGF production, but the results of Part II suggest that CsA acts to block ICGF activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Streptozotocin interactions with pancreatic beta cells and the induction of insulin-dependent diabetes

The MSZ diabetic male mouse represents one of the most useful tools available to researchers interested in analyzing the consequences of insulin dependent diabetes in male mice. In contrast to the high mortality induced by single high doses of SZ, protracted administration of smaller SZ dosages yields a more stable diabetic condition. Moreover, in insulitis prone strains such as BKs, the model allows "synchronization" of beta cell destruction such that the inflammatory events occur on a predictable timescale. The MSZ-diabetic mouse represents a diabetic condition in which the primary etiopathologic effect is produced by an environmental toxin, and not by a genetically programmed loss of tolerance to beta cell specific antigens. In this regard, etiopathogenesis in the MSZ model is quite distinct from that underlying autoimmune type I diabetes in humans, NOD mice, and BB rats, and it is probably not appropriate to refer to pathogenesis in the MSZ model as one of "autoimmune insulitis" as has sometimes been done. The fact that insulitis in the MSZ model may not be "autoimmune," but may actually be a normal response to either tissue damage or to beta cells that have been structurally modified by a chemical, makes the model of special interest. Clearly, there is no single cause of insulin dependent diabetes, with disease induction representing a genetic susceptibility interacting with environmental triggers, such as toxins in the diet (including nitrosamines and fungal metabolites) as well as pathogenic viruses. The MSZ model will continue to be actively investigated because of insights it will afford regarding the genetic bases for susceptibility and resistance to diabetogenic environmental toxins. The model will be of further value by contributing to knowledge of the complicated interactions between pancreatic islet cells, other endocrine cells, and leukocytes in maintenance of glucose homeostasis.

Endocrine and metabolic abnormalities following kidney transplantation

Various endocrine and metabolic disturbances associated with long standing uremia persist after kidney transplantation or arise from the use of immunosuppressive drugs. Hyperlipidemia for long time being implicated as the cause of corticosteroids is also observed in renal transplant recipients treated with cyclosporin A monotherapy. After conversion from cyclosporin to azathioprine serum cholesterol and triglyceride concentration fall, and elevation of LDL-cholesterol may also be reversed. There is a tendency for higher HDL-cholesterol in azathioprine and prednisolone treated transplant patients. Those patients who are at risk for clinically significant cholesterol elevations can be predicted by their pretransplant lipid levels, specifically the LDL-fraction. Risk-benefit ratio of conversion and of treatment with lipid-lowering drugs, especially with lovastatin, should be carefully examined, also in view of glucose intolerance. Higher incidence of diabetes mellitus requiring insulin therapy in cyclosporin treated transplant recipients has been reported. Cyclosporin may cause toxic effects on pancreatic beta-cells resulting in inhibition of insulin secretion. High doses of cyclosporin induce inhibition of glycogen synthesis in rat liver. Glucose intolerance is reversible after reduction of cyclosporin dose or conversion to azathioprine. Therefore glucose metabolism in kidney transplant recipients treated with cyclosporin should be carefully followed. Immunosuppressive therapy may affect reproductive function, arachidonate metabolism and renin-angiotensin-aldosterone system as well as posttransplant calcium and phosphate metabolism. Endocrine and metabolic abnormalities are associated with long standing uremia. After successful kidney transplantation several observations are normalized but further complications arise from the use of immunosuppressive drugs. The present paper reviews various endocrine and metabolic disturbances described following renal transplantation.

Prednisone, azathioprine, and cyclosporine A toxicity on human fetal pancreas

The limited clinical success of human fetal pancreas (HFP) transplantation may be related to graft toxicity caused by immunosuppressant agents. This study describes the effects of prednisone (PRED), azathioprine (AZA), and cyclosporine A (CSA) on HFP tissue in vitro and in vivo. To assess in vitro function, fresh HFP explants (1-2 mm3; 16-21 weeks gestational age) were prepared and cultured 72 hr in supplemented Ham's medium containing varying concentrations of each drug. Insulin release in response to high glucose (17 mM) and theophylline (10 mM) challenge was determined and compared to basal release in low glucose (3 mM) buffer. No significant difference in insulin release was observed between culture control tissue and drug-cultured tissue throughout the concentration range (10(-8) -10(-4) M; P greater than 0.05). To assess in vivo function, cyropreserved HFP explants were transplanted under the kidney capsule of streptozotocin-induced diabetic nude mice. Mice were immunosuppressed with PRED (1 mg/kg), AZA (1 mg/kg), CSA (30 mg/kg), or combined triple drug therapy (COMBO), and glucose levels followed weekly. Hyperglycemia reversal and insulin withdrawal were observed in all drug groups [PRED (4/6), AZA (4/6), CSA (2/4), COMBO, (2/4)] and were not statistically different from control (5/8; P greater than 0.8). Time to insulin withdrawal was significantly different from control (12.2 +/- 2.2 weeks; P less than 0.05) only for AZA (10 +/- 0 weeks; PRED, 12.3 +/- 2.6 weeks; CSA, 11 +/- 0 weeks; COMBO, 15 +/- 0 weeks). Additionally, oral glucose tolerance tests in all groups were equivalent to nondiabetic controls. We were unable to demonstrate PRED, AZA, or CSA toxicity on HFP.(ABSTRACT TRUNCATED AT 250 WORDS)