Pretreatment of donor islets with the Na(+) /Ca(2+) exchanger inhibitor improves the efficiency of islet transplantation.

Pancreatic islet transplantation is an attractive therapy for the treatment of insulin-dependent diabetes mellitus. However, the low efficiency of this procedure necessitating sequential transplantations of islets with the use of 2-3 donors for a single recipient, mainly due to the early loss of transplanted islets, hampers its clinical application. Previously, we have shown in mice that a large amount of HMGB1 is released from islets soon after their transplantation and that this triggers innate immune rejection with activation of DC, NKT cells and neutrophils to produce IFN-γ, ultimately leading to the early loss of transplanted islets. Thus, HMGB1 release plays an initial pivotal role in this process; however, its mechanism remains unclear. Here we demonstrate that release of HMGB1 from transplanted islets is due to hypoxic damage resulting from Ca(2+) influx into ß cells through the Na(+) /Ca(2+) exchanger (NCX). Moreover, the hypoxia-induced ß cell damage was prevented by pretreatment with an NCX-specific inhibitor prior to transplantation, resulting in protection and long-term survival of transplanted mouse and human islets when grafted into mice. These findings suggest a novel strategy with potentially great impact to improve the efficiency of islet transplantation in clinical settings by targeting donor islets rather than recipients.

CD4(+) Valpha14 natural killer T cells are essential for acceptance of rat islet xenografts in mice.

Pancreatic islet transplantation represents a potential treatment for insulin-dependent diabetes mellitus. However, the precise cellular and molecular mechanisms of the immune reactions against allogeneic and xenogeneic transplanted islets remain unclear. Here, we demonstrate that CD4(+) Valpha14 natural killer T (NKT) cells, a recently identified lymphoid cell lineage, are required for the acceptance of intrahepatic rat islet xenografts. An anti-CD4 mAb, administrated after transplantation, allowed islet xenografts to be accepted by C57BL/6 mice, with no need for immunosuppressive drugs. The dose of anti-CD4 mAb was critical, and the beneficial effect appeared to be associated with the reappearance of CD4(+) NKT cells at around 14 days after transplantation. Interestingly, rat islet xenografts were rejected, despite the anti-CD4 mAb treatment, in Valpha14 NKT cell-deficient mice, which exhibit the normal complement of conventional lymphoid cells; adoptive transfer of Valpha14 NKT cells into Valpha14 NKT cell-deficient mice restored the acceptance of rat islet xenografts. In addition, rat islet xenografts were accepted by Valpha14 NKT mice having only Valpha14 NKT cells and no other lymphoid cells. These results indicate that Valpha14 NKT cells play a crucial role in the acceptance of rat islet xenografts in mice treated with anti-CD4 antibody, probably by serving as immunosuppressive regulatory cells.

Intratesticular transplants of islet xenografts (rat to mouse).

Freshly isolated rat islets were transplanted into the testis of diabetic mice. The intratesticular islet xenografts produced normoglycemia in the diabetic recipients. The survival time of the intratesticular xenografts was significantly longer than intrasplenic, intrahepatic, and renal subcapsular sites of transplantation of xenografts of freshly isolated rat islets. Three of the recipients with intratesticular islet grafts were still normoglycemic at 60 days after transplantation, and orchidectomy resulted in a return to the diabetic state. The findings indicate that the testis provided a more privileged immunologic site than either the spleen, liver, or kidney and the lower temperature of the testis apparently did not affect the function of the islet grafts since the recipients became normoglycemic.

An improved method for the isolation of islets from the beef pancreas.

An improved method for the isolation of islets from the beef and pig pancreas is described. The procedure involves the use of strips of Velcro that retain the partially-digested collagen during the isolation of islets by the collagenase technique. The spiny portion of the Velcro is ideally suited to retain the collagen and yet permit the separation of islets from the pancreatic parenchyma. A remarkably high yield of islets has been obtained from the beef and pig pancreas using this procedure.

The start of an islet transplantation program in Japan.

In Japan, pancreas donation had become possible from cadaveric donor sources, both heart-beating or non-heart-beating (NHB). Pancreas allografts have been distributed in the organ allocation system of the Japan Organ Transplant Network. Meanwhile, islet transplantation has been categorized as a tissue transplantation; it is free from legal restraints. Thus, pancreata for islet isolation must be obtained from NHB donors. Herein we report the starting program and preliminary results of islet transplantation in Japan. Selection and listing criteria for transplantation include regional priority, ABO blood type, previous islet transplant status with insulin independence, and a longer waiting time. Five institutes in Japan (Fukushima, Chiba, Kyoto, Kobe, and Fukuoka) are prepared to start programs. A two-layer cold storage method using perfluorocarbons and UW solution is recommended for pancreas preservation. Islet isolation and purification procedures are performed according to institute-specific protocol. Immunosuppression is based on sirolimus/tacrolimus combined with basiliximab induction. Two or three consecutive infusions of >5000 IE/kg are planned for each recipient until achieving insulin independence. Twenty-seven isolations and 14 transplants were performed in eight non-insulin-dependent diabetes mellitus (IDDM) recipients. Almost all (26 of 27) were NHB donors. All recipients are free from hypoglycemic episode after transplantation. One of these recipients is insulin independent; the others are currently on minimal doses of exogenous insulin. The feasibility of islet transplantation using NHB donors was confirmed using a two-layer cold storage method and a steroid-free immunosuppressive protocol, with a high rate of graft function.

Long-term acceptance of allografts by in vivo gene transfer of regulatable adenovirus vector containing CTLA4IgG and loxP.

CTLA4IgG was shown to inhibit the costimulatory signal for T cell activation by interfering with the ligation of CD28 and B7-1 or B7-2. To inhibit various immune responses including acute cellular rejection of allografts, a certain level of serum CTLA4IgG should be maintained for an appropriate period. We previously reported on an adenovirus vector containing CTLA4IgG, which we designated Adex1CACTLA4IgG. Adex1CACTLA4IgG was able to maintain a significant level of serum CTLA4IgG for a long period on intravenous injection, which in turn inhibited various immune responses including protective immunity against infectious agents. To overcome the inhibitory effect, we constructed a new adenovirus vector, Adex1CALoxCTLA4IgGLox, by cloning CTLA4IgG cDNA between two loxP sequences under the control of the CAG promoter. We demonstrated that the administration of adenovirus vector containing Cre recombinase gene (Adex1CACre) at the desired time induced Cre-mediated recombination within a gene derived from Adex1CALoxCTLA4IgGLox vector, and the cDNA of CTLA4IgG was excised from the transduced gene and terminated the expression of CTLA4IgG in vitro and in vivo. More importantly, we also demonstrated that the long-term acceptance of allografts was achieved after the termination of CTLA4IgG expression, while the immune response against adenovirus was restored.

In vitro study of cultured human insulinoma cells: evidence of abnormal sensitivity to glucose.

Human insulinoma cells were isolated and cultured in vitro, and their functional and morphological characteristics were determined. The cells, isolated as single cells or small cell clusters, reaggregated to almost the size of islets by the fifth culture day and were maintained in vitro for more than 1 month. Morphologically (light and electron microscopies) they were intact throughout the culture period. Immunohistochemically more than 50% of the cells in each reaggregate contained insulin. Incubation experiments revealed that a low glucose concentration (15 mg/dL) was sufficient to produce maximal insulin release. In the absence of glucose, 1 microgram/mL glibenclamide increased insulin release. On the other hand, 5 mM theophylline and 10 mM arginine did not alter insulin release significantly. Theophylline, arginine, and glibenclamide did not have any stimulatory effect on insulin release in the presence of 50 mg/dL glucose. Perifusion experiments with 50 mg/dL glucose disclosed a biphasic pattern of insulin release, and no significant change in insulin release occurred when the glucose concentration in the perifusate was switched from 50 to 150 and then back to 50 mg/dL. These findings demonstrate that human insulinoma cells can be isolated and maintained in vitro and that the cells have abnormal sensitivity to glucose.

The necessity of differential immunosuppression for prevention of immune rejection by FK506 in rat islet allografts transplanted into the liver or beneath the kidney capsule.

The purpose of the present study was to achieve prevention of immune rejection in rat islet allografts by FK506. WKA/Qdj (RT1u) islets were transplanted either into the liver via the portal vein (p.v.) or beneath the kidney capsule (k.c.) of streptozotocin (60 mg/kg) induced diabetic Lewis (RT1(1)) rats. Fresh or cultured (24 degrees C, 1 week) islets were used as donors. A miniosmotic pump (0.2 ml, Alzet 2001) containing 5 mg FK was implanted s.c. at the time of transplantation for continuous delivery of FK506 for 7 days after transplantation. The mean survival time (MST) of the fresh p.v. grafts with a pump was offater than 61.4 +/- 37.2 days (mean +/- SD, n = 17) (control 5.5 +/- 0.6, n = 4). Ten out of 17 were normoglycemic for more than 90 days after transplantation. When low-temperature cultured islets were used and FK506 was delivered for 7 days, all the rats were normoglycemic for more than 90 days after transplantation. The MST of the fresh or cultured k.c. grafts with a pump was 22.0 +/- 14.2 or 24.7 +/- 5.0 days, respectively. Long-term administration of FK506 by repeated implantations (5 times; days 0, 7, 14, 21, and 28) of pumps containing 5 mg FK506 produced marked prolongation of the fresh or cultured k.c. graft survival with an MST of greater than 58.7 +/- 22.1 or greater than 56.9 +/- 18.0 days, respectively. These findings clearly demonstrate that the prevention of immune rejection in the islet allografts transplanted into the liver was achieved by short-term post-transplant administration of FK506 and low-temperature culture of donor islets, and also show that long-term continuous administration of FK506 was needed for the prolongation of the graft survival when the renal subcapsular space was the site for implantation of islets. Thus, the present study indicates that in different transplant sites different immunosuppressive regimes are needed for the control of rejection by FK506 in rat islet allografts.

FK506 as the sole immunosuppressive agent for prolongation of islet allograft survival in the rat.

The purpose of the present study was to determine immunosuppressive effects of a new immunosuppressive agent, FK506, on rat islet allografts and also whether FK is toxic to the islet grafts since the diabetogenic effects of FK is controversial. Hand-picked clean fresh islets (WKA/Qdj:RT1u) were transplanted either beneath the renal capsule or into the liver via the portal vein of the diabetic (STZ, 60 mg/kg) rats (Lewis:RT1(1)). FK506 was administered s.c. for 7 days after transplantation. The mean survival times (MST)* of the renal subcapsular grafts receiving 0 (control), 0.32 or 1.0 mg/kg FK were 7.2 +/- 1.1 (mean +/- SD, n = 5), 13.8 +/- 4.8 (n = 4), and 20.2 +/- 8.0 days (n = 5), respectively. The MST of the intrahepatic grafts receiving 0, 0.1, 0.32, or 1.0 mg/kg FK were 4.4 +/- 1.1 (n = 5), 7.2 +/- 0.8 (n = 5), greater than 45.3 +/- 23.1 (n = 6) or greater than 54.4 +/- 8.8 days (n = 5), respectively. Histologically, islets were found easily in the liver of normoglycemic recipients for more than 60 days after transplantation and appeared intact, with well-granulated beta cells. Foci of mononuclear cells were occasionally seen adjacent to the islet cells. The plasma glucose of the recipients with 1.0 mg/kg FK fluctuated between 150 and 350 mg/dl without rejection. In the recipients treated with 3.2 mg/kg FK the plasma glucose of all the recipients (n = 3) returned to pretransplant levels by 21 days after transplantation. However, islet cells were present in the liver of all these recipients without mononuclear cell infiltration. Immunohistochemically islet grafts stained weakly for insulin, but to the same extent as the controls for glucagon and somatostatin. These findings clearly demonstrate the immunosuppressive effect of FK506 on islet allografts and the importance of the transplant site for prolongation of graft survival by FK, and also suggest that FK has toxic effects on the islet grafts (B cells) when used in high dosages.

A new site for islet transplantation--a peritoneal-omental pouch.

A new site for islet transplantation is described. A peritoneal-omental pouch was constructed in diabetic rats by encasing the omentum in a pouch formed from a strip of parietal peritoneum obtained from the recipient. Isografts of rat islets placed in the pouch maintained normoglycemia in the recipients and removal of the pouch resulted in a rapid return to a diabetic state. This site may be applicable to the transplantation of islets in human diabetes.

Prolongation of islet xenograft survival (rat to mouse) by in vitro culture at 37 C.

Meticulously selected rat islets were maintained in vitro for 7 days in a minimal volume of tissue culture medium at 37 C in air and 5% CO2. The cultured islets were transplanted into diabetic mice, either into the liver via the portal vein, or beneath the renal capsule. The survival of the cultured islets, following intrahepatic or renal subcapsular transplantation, was significantly prolonged compared with that of fresh islets. The renal subcapsular site apparently provides some additional immunologic advantage, because the survival time of the cultured islets in this site was approximately twice as long as in the intrahepatic transplants.

The amelioration of hyperglycemia in streptozotocin-induced diabetic rats after the intraportal transplantation of an insufficient number of islets by nicotinamide treatment.

The purpose of the present study was to determine whether or not hyperglycemia in streptozotocin (STZ)-induced diabetic rats after the intraportal transplantation of an insufficient number of isogenic islets can be ameliorated by nicotinamide treatment. WKA/Qdj (RT 1u) rats were used both as donors and recipients. Islets were isolated by the collagenase technique. A total of 350 islets was transplanted into the liver via the portal vein of the STZ-induced diabetic rats. Either nicotinamide (NA, 0.5 g/kg) or a vehicle (saline) was administered ip once a day for 60 days after transplantation. All the diabetic rats without islet transplantation remained hyperglycemic irrespective of the NA treatment. All the recipients (n = 12) bearing the islet grafts and treated with saline remained hyperglycemic (> 400 mg/dl) at 60 days after transplantation. In marked contrast, all the recipients (n = 18) with islet grafts and treated with NA became normoglycemic (< 200 mg/dl) at 16.2 +/- 7.1 days (mean +/- SD) after transplantation. Morphologically, islets were easily found in the liver of the recipients. Aldehyde-fuchsin stain revealed that the beta cells in the islet grafts of the NA treated recipients were well granulated, whereas those treated with saline were degranulated. The insulin content of the liver bearing the grafts treated with either NA or saline was 116.3 +/- 26.0 micrograms/liver (n = 4) or 5.7 +/- 2.2 micrograms (n = 4), respectively, while that of 350 donor islets was 29.4 +/- 2.5 micrograms (n = 5). The insulin content of the pancreas in the NA- or saline-treated recipients was 27.3 +/- 10.6 micrograms/pancreas (n = 4) or 2.7 +/- 1.2 micrograms (n = 4), respectively, while those of the pancreas from the diabetic rats without transplantation was 1.9 +/- 0.7 micrograms (n = 4) or 1.6 +/- 0.8 micrograms (n = 5), respectively. These findings clearly demonstrate that the hyperglycemia in the STZ-diabetic recipients after transplantation of an insufficient number of islets can be ameliorated while, in addition, the islet mass in the liver as well as the endogenous pancreas both increase in size with nicotinamide treatment.

Hepatocyte growth factor is essential for amelioration of hyperglycemia in streptozotocin-induced diabetic mice receiving a marginal mass of intrahepatic islet grafts.

BACKGROUND: It is crucial for clinical islet transplantation to find a procedure to improve the success rate of insulin independence after islet transplantation. In the present study, we determined whether hepatocyte growth factor (HGF) has a favorable effect on amelioration of hyperglycemia in streptozotocin (STZ, 200 mg/kg)-induced diabetic mice (C57BL/6) receiving a marginal mass of intrahepatic islet isografts. METHODS: Isolated syngeneic islets were transplanted into the liver of recipients. HGF with dextran sulfate (DS) was administered intraperitoneally once a day at day 0, 2, 4, 6, and 8 relative to islet transplantation. DS has been known to enhance the effect of HGF. RESULTS: It was found that the number of 250 islets was a marginal mass as donor islets in this model, in which 2 out of 14 diabetic mice receiving 250 islets became normoglycemic by 90 days after transplantation. The treatment with HGF (100 microg) in conjunction with DS (200 microg) produced normoglycemia in all mice (n = 5). Morphological study as well as intraperitoneal glucose tolerance test revealed the beneficial effects of HGF. To our surprise, six out of nine mice receiving 250 islets and treated with DS alone became normoglycemic. Additional anti-HGF antibody treatment (100 microg, day -1, 0, 2, 4, 6, and 8) abolished the effects of DS, indicating that the effect by DS is mediated via the endogenous HGF. The effects of DS were not observed when the renal subcapsular space was the site of islet transplantation. There was a significant increase in plasma HGF levels in mice after the intrahepatic grafts but not the renal subcapsular one. CONCLUSIONS: These findings demonstrate that HGF is essential for amelioration of hyperglycemia in STZ-induced diabetic mice when a marginal mass of islets was grafted into the liver. As the liver is the site of clinical islet transplantation and the inability to achieve insulin independence after transplantation is a major obstacle for successful transplantation, HGF may facilitate to overcome such an important issue for clinical islet transplantation.

Effect of troglitazone on blood insulin levels after pancreas transplantation with systemic venous drainage in rats.

BACKGROUND: Troglitazone is a new oral antidiabetic agent and has been reported to reduce insulin resistance and improve peripheral hyperinsulinemia in patients with noninsulin-dependent diabetes mellitus. To examine the effect of troglitazone on insulin regulation after pancreas transplantation with systemic venous drainage, we measured peripheral glucose and insulin levels and performed an intravenous glucose tolerance test. METHODS: We divided the rats into four groups: diabetic rats with a pancreas graft and administration of troglitazone at 40 mg/day orally (group P+T, n=4), rats with a pancreas graft only (group P, n=4), age-matched normal rats (group N, n=5), and diabetic rats (group DM, n=4). RESULTS: Fasting insulin levels in group P were relatively higher than those in group N, whereas the values in group P+T were normalized. In the intravenous glucose tolerance test, troglitazone clearly regulates sigma immunoreactive insulin levels of pancreas transplanted rats (P vs. P+T: 244+/-23 vs. 145+/-14 microU/ml, P<0.05). CONCLUSION: Hyperinsulinemia induced by systemic venous drainage, which may progress atherosclerosis, can be controlled with troglitazone treatment.

Expansion of intermediate T cell receptor cells expressing interleukin-2 receptor alpha- beta+, CD8alpha+ beta+, and lymphocyte function-associated antigen-1+ in the liver in association with intrahepatic islet xenograft rejection from rat to mouse: prevention of rejection with anti-interleukin-2 receptor beta monoclonal antibody treatment.

BACKGROUND: The precise mechanisms involved in islet xenograft rejection remain unknown. The purpose of the present study was to determine cellular mechanisms responsible for islet xenograft rejection in the liver to facilitate finding a procedure for prevention of immune rejection. METHODS: Hepatic mononuclear cells (MNC) as well as splenocytes, peripheral blood MNC, and thymocytes from streptozotocin-induced diabetic mice (BALB/c) rejecting the intrahepatic rat (Lewis) islet xenografts were isolated and examined by two-color FACS analysis. RESULTS: The characteristic finding of the hepatic MNC from the mice rejecting islet xenografts compared with mice receiving isografts was a significant increase in the yield as well as in the percentage of the cells expressing CD3+ interleukin-2 receptor (IL-2R) alpha- beta+, CD3+ CD8alpha+ beta+, and T cell receptor (TCR) alphabeta+ lymphocyte function-associated antigen-1+. The expression of CD3 and TCR alphabeta of these T cells was found to be of intermediate intensity (TCR(int) cells). The expansion of these TCR(int) cells occurred predominantly in the liver. There was no significant difference in the cells expressing CD3+ IL-2R alpha+, CD3+ CD4+, CD3+ TCRgammadelta+, CD3- IL-2Rbeta+ (natural killer cells), and B220+ (B cells). In vivo administration of anti-IL-2Rbeta monoclonal antibody directed to the expanded cells produced a prevention of rejection. CONCLUSIONS: These findings suggest that islet xenograft rejection in the liver from rat to mouse is an event for which the TCR(int) cells are responsible.

Lymphoepithelial cyst of the pancreas in a 65-year-old man.

A case of an extremely rare cystic lesion of the pancreas is presented. The multilocular cyst was found adjacent to the upper border of the pancreatic body, and the cyst contained bean curd lees-like substances. Histologically, the cyst wall consisted of mature keratinizing squamous epithelium and surrounding lymphoid tissue stroma, and the cyst was filled with keratinized materials. A histopathologic diagnosis of typical lymphoepithelial cyst of the pancreas, proposed by Truong et al (Am J Surg Pathol 11:899-903, 1987), was made. Its histogenesis is still unknown; however, we hypothesize that it might arise from a benign epithelial inclusion of a peripancreatic lymph node, followed by squamous metaplasia of the epithelial inclusion. We recently found a retropyloric lymph node with a squamous epithelial inclusion, which might support this hypothesis regarding the histogenesis of the cyst.

In vitro release of vasoactive intestinal polypeptide and pancreatic polypeptide from human VIPoma cells and its inhibition by somatostatin analogue (SMS 201-995).

BACKGROUND: The purpose of the present study was to determine whether vasoactive intestinal polypeptide (VIP) is released from the tumor cells of VIPoma and if so then to attempt to show how its release is regulated by cultured human VIPoma cells. METHODS: A resected specimen of a pancreatic tumor from a patient with watery diarrhea, hypokalemia, and achrohydria syndrome was examined. The dissociated cells were obtained by collagenase digestion of the tumor tissue and were cultured in vitro. RESULTS: The extraction of tumor cells disclosed that the cells contained VIP and pancreatic polypeptide (PP). Neither insulin, glucagon, somatostatin nor pancreastatin was detected. Immunohistochemically, 40% to 60% of the cells in the tumor stained positively for VIP and 1% to 5% stained positively for PP. The dissociated cells became reaggregated in the culture (50 to 300 microns) and could be maintained in vitro. Incubation experiments revealed a simultaneous in vitro release of VIP and PP with a significant increase by either carbachol or phorbol myristate acetate but not by theophylline or caerulein. Atropine completely abolished the stimulatory effects of carbachol on VIP and PP release. Octreotide (somatostatin analogue [SMS 201-995]) significantly inhibited the carbachol and phorbol myristate acetate-stimulated VIP and PP release. CONCLUSIONS: These findings show the in vitro release of VIP and PP from the VIPoma cells and also provide evidence for the direct inhibitory effect of somatostatin analogue on both the VIP and PP release from the tumor cells.

Donor-specific unresponsiveness induced by intraportal grafting and FK506 in rat islet allografts: importance of low temperature culture and transplant site on induction and maintenance.

Previously we demonstrated prolongation of islet allograft survival in rat by administration of FK506 to the recipients. The purpose of the present study was to determine whether specific immune unresponsiveness had been induced and to determine the effects of low temperature culture of donor islets as well as the transplant site on the induction of immune unresponsiveness. At 90 days after transplantation, normoglycemic recipients bearing functional intrahepatic grafts were made diabetic again with streptozotocin (STZ) and donor specific or third party islets were transplanted either into the liver or beneath the kidney capsule. When fresh islets were used as donors in initial transplantation in conjunction with FK506, intrahepatic re-transplants of fresh islets from the donor-specific strain in the absence of FK506 maintained normoglycemia for more than 60 days, while third party transplants (n = 3) were rejected within 1 wk. In contrast to intrahepatic regrafts, all the renal subcapsular regrafts from the donor-specific strain (n = 3) were rejected with mean survival time of 12.7 +/- 6.4 days. When cultured (24 degrees C, 7 days) islets were used for initial transplantation in conjunction with FK506, re-transplants of fresh or cultured islets from the donor specific strain beneath the kidney capsule maintained normoglycemic in 3 out of 6 or all (n = 4) of the recipients, respectively. Cultured third party regrafts beneath the kidney capsule (n = 2) were rejected at 9 days.(ABSTRACT TRUNCATED AT 250 WORDS)

Rat pancreastatin inhibits both pancreatic exocrine and endocrine secretions in rats.

Effects of synthetic rat pancreastatin C-terminal fragment on both exocrine and endocrine pancreatic functions were examined in rats, in vivo and in vitro. Pancreastatin (20, 100 pmol, 1 nmol/kg/h) significantly inhibited CCK-8-stimulated pancreatic juice flow and protein output in a dose-related manner, in vivo. The inhibitory effect on bicarbonate output was not statistically significant. Pancreastatin did not significantly inhibit basal pancreatic secretions in vivo, and did not inhibit amylase release from the dispersed acini, in vitro. Insulin release stimulated by intragastric administration of glucose (5 g/kg) was significantly inhibited by pancreastatin (1 nmol/kg/h), in vivo. Plasma glucose concentrations were increased by pancreastatin infusion, but the increase was not statistically significant. Furthermore, pancreastatin inhibited insulin release from isolated islets, in vitro. Synthetic rat C-terminal pancreastatin fragment has bioactivities on both exocrine and endocrine pancreatic functions in rats.

Amelioration of hyperglycemia in streptozotocin-induced diabetic rats receiving a marginal mass of islet grafts by troglitazone, an oral antidiabetic agent.

Troglitazone, a novel oral antidiabetic agent, was evaluated to determine whether it could have hypoglycemic effects in streptozotocin (STZ)-induced diabetic rats when a marginal mass of islets was transplanted and hyperglycemia persisted after transplantation. Lewis rats (RT1(1)) were used as both donors and recipients. Five hundred fresh islets were transplanted beneath the kidney capsule of STZ-induced diabetic recipients. Troglitazone was administered orally (0.34 mmol/kg/day) for 7 days before and for 60 days after islet transplantation. Neither troglitazone treatment without islet transplantation (n = 8) nor islet transplantation alone (n = 7) could produce normoglycemia (< 11 mmol/L) in diabetic recipients by 60 days after transplantation. In marked contrast, seven of 10 rats receiving islet grafts and treated with troglitazone became normoglycemia at 26.9 +/- 16.4 days (mean +/- SD; n = 7) after transplantation. Removal of the kidney bearing the grafts promptly resulted in the normoglycemic recipients (n = 4) becoming diabetic again. Light and electron microscopically, the intact islets with well-granulated beta cells could be observed in the transplant site of the normoglycemic recipients. These findings clearly demonstrate that the hyperglycemia in STZ-induced diabetic rats receiving an insufficient number of islet grafts to reverse diabetes was ameliorated by troglitazone treatment.