Altered phosphorylation state of branched-chain 2-Oxo acid dehydrogenase in a branched-chain acyltransferase deficient human fibroblast cell line

Summary The abundance and phosphorylation state of the polypeptide constitutents of the human branched-chain 2-oxo acid dehydrogenase complex were examined in mitochondria from normal and maple syrup urine disease (MSUD) fibroblasts. In normal fibroblast mitochondria two forms of the E₁ subunit were observed: non-phosphorylated (E₁) and phosphorylated (E_1–P). About 40–50% of E₁ was present as E_1–P. The ability to quantitate the two forms of E₁ permitted examination of the association between decreased capacity to oxidize branched-chain 2-oxo acids and the phosphorylation state of E₁.Changes in phosphorylation state of E₁ were observed in MSUD fibroblasts as compared to control cells. Of particular interest was the absence of E_1–P in an MSUD fibroblast line which lacked the dihydrolipoyl acyltransferase (E₂) subunit of the dehydrogenase complex. In two MSUD cell lines deficient in E₁, the abundance of E_1–P appeared to be preferentially reduced. A fourth MSUD cell line contained normal quantities of E₃, E₂ and both forms of the E₁ polypeptide. Our results indicate that alterations in the abundance of dehydrogenase complex polypeptides in MSUD fibroblasts may influence the phosphorylation state of the E₁ polypeptide. They demonstrate the potential for examining simultaneously mutations which affect both the catalytic and regulatory components of the dehydrogenase complex.     

Gene analysis of mennonite maple syrup urine disease kindred using primer-specified restriction map modification

Summary Maple syrup urine disease (MSUD) is an autosomal recessive inherited disease due to a deficiency of any of the subunits, E₁, E₁ or E₂, of the branched-chain -ketoacid dehydrogenase complex (BCKDH). A large Mennonite kindred of MSUD has been studied in Pennsylvania, USA. In the present investigation, genomes from 70 members, including 12 patients belonging to eight different Mennonite MSUD pedigrees, were examined for possible abnormalities in the E₁ gene of BCKDH, by primer-specified restriction map modification. A T-to-A substitution which generates an asparagine in place of a tyrosine at amino acid 394 of the mature E₁ subunit was present in both alleles in all the patients and in a single allele in all obligate carriers and several siblings. We describe a new technique for rapid and easy detection of the mutant gene in this population. These family studies provide additional evidence that Mennonite MSUD is caused by a missense mutation of the E₁ gene of BCKDH.     

Maple syrup urine disease: mutation analysis in Turkish patients

Maple syrup urine disease (MSUD), the most frequently occurring organic acidaemia in Turkey, is caused by a deficiency of the activity of branched-chain keto acid dehydrogenase enzyme (BCKAD) complex. Mutation analysis of the E1, E1, and E2 genes of the BCKAD complex in 12 Turkish MSUD patients yielded three disease-specific mutations and a polymorphism in the E1 gene, none in the E1 gene and one mutation in the E2 gene. Among them, three missense mutations (Q80E, C213Y, T106M) and the F280F polymorphism occurring in the E1 gene and the splice site mutation (IVS3 – 1G > A) in the E2 gene were novel. Three of the missense mutations and the splicing mutation occurred homozygously and caused classical MSUD. One patient carried the splicing mutation homozygously and the T106M mutation in the heterozygous state; this patient is the first case having simultaneously two different mutations in two different genes in the BCKAD complex. IVS3 – 1G > A splicing mutation detected on the E2 gene causes deletion of the first 14 bp of exon 3 in the mutant mRNA extending between 190 and 204 nt. The deletion spans the cleavage point between mitochondrial targeting and lipoyl-bearing site of the E2 protein.     

Low Endogenous Prostaglandin E2 Predisposes to Relapsing Inflammation in Experimental Rat Enterocolitis

Intramural injection ofpeptidoglycan-polysaccharide (PG-PS) induces acuteenterocolitis that spontaneously relapses in Lewis butnot Fischer rats. Interleukin-1 (IL-1) and tumornecrosisfactor- (TNF-) induce prostaglandin E₂(PGE₂) secretion, which inhibits secretion ofthese cytokines by macrophages, suggesting an inhibitoryfeedback mechanism. We postulate that Lewis ratsusceptibility to relapse is due to an imbalance betweenprotective prostaglandins and cytokines. Female Fischerand Lewis rats were injected with PG-PS (37.5 g/g)or human serum albumin intramurally. Tissue IL-1 and PGE₂ immunoreactivities andmyeloperoxidase (MPO) activity were determined.Relapsing rats had lower PGE₂ andPGE₂:IL-1 ratios than nonrelapsingrats (P < 0.05). In Fischer rats, 2 mg/kg/day indomethacinpotentiated cecal MPO and IL-1 concentrationsabove PG-PS alone (P < 0.05). Misoprostol treatmentblocked PG-PS-induced IL-1 and MPO and inhibited the potentiating effect of indomethacin on MPOand IL-1 (P < 0.05). In conclusion, increasedendogenous PG may be protective against relapsinginflammation in PG-PS induced enterocolitis, at least partially via inhibition of proinflammatorycytokines. An imbalance between protectiveprostaglandins and proinflammatory cytokines may beinvolved in the pathogenesis of chronic relapsinginflammation in genetically susceptible hosts.     

Interferonγ and tumour necrosis factorα induce a synergistic antiproliferative response in human Ewing's sarcoma cells in vitro

Three human cell lines derived from Ewing's sarcoma (RM-82, VH-64, and WE-68) were investigated to establish the influence of recombinant human interferon (rhIFN) and tumour necrosis factor (rhTNF) on cell proliferation and survival and to characterize IFN and TNF receptor expression. Incorporation of [³H]thymidine into cells was inhibited by rhIFN after 24 h of incubation. Half-maximal inhibition was observed with 10–80 U/ml rhIFN. A maximal effect (50%–70% inhibition of cell proliferation) was achieved by treatment of cells with 250 U/ml rhIFN. The influence of rhTNF on proliferation was found to differ among cell lines and varied with the concentration and the duration of exposure of cells to this cytokine. In WE-68 and VH-64 cells [³H]thymidine incorporation was not affected by rhTNF up to 2000 U/ml after 96 h of incubation, where-as in RM-82 cells the incorporation was inhibited by 35% after 48 h of incubation with 100 U/ml rhTNF. However, all cell lines showed a synergistic antiproliferative response to the combination of rhIFN and rhTNF after 24 h of incubation. The human recombinant cytokines interleukin(IL)-1, IL-1, IL-2, IL-3, IL-4, IL-6 and granulocyte/macrophagecolony-stimulating factor, tested alone and in combination with rhIFN and rhTNF, had no influence on cell proliferation. Binding studies in the cell lines with¹²⁵I-rhIFN revealed a dissociation constant (K _d ) of 160–306 pM and approximately 8000–13500 receptors/cell. Binding experiments with¹²⁵I-rhTNF indicated 430–1250 receptors/cell withK _d ranging from 13 pM to 162 pM. These data indicate that, among various cytokines, only IFN and TNF are capable of potently reducing Ewing's sarcoma cell growth in vitro. Our data suggest that IFN alone or in combination with TNF may be useful in the design of novel strategies in Ewing's sarcoma therapy.     

A case of PDH-E1α mosaicism in a male patient with severe metabolic lactic acidosis

We have characterized a novel mutation in a male patient that affects the coding sequence of PDH-E₁ gene and changes arginine-141 to a leucine. This nucleotide substitution was found in about 75% of the studied DNA (fibroblasts, liver and muscle), a scenario that would indicate a case of E₁ mosaicism in a male patient. When the mutant E₁ protein was expressed in human skin fibroblasts with zero endogenous pyruvate dehydrogenase complex activity and E₁ protein expression, no significant restoration of activity was recorded, in contrast to the wild-type cDNA, even though both wild-type and mutant protein levels were comparable. We concluded that the R141L mutation is a severe one and that it must have occurred in one of the E₁ alleles during early embryogenesis.     

Adrenergic regulation of the rapid component of the cardiac delayed rectifier potassium current,I<Subscript>Kr</Subscript>, and the underlying hERG ion channel

Abstract. Ventricular arrhythmias are often precipitated by physical or emotional stress, in particular in patients with ischemic heart disease or hereditary long QT syndrome. Stimulation of the sympathetic nervous system in response to exercise or emotional stress causes activation of cardiac - and -adrenoceptors. The rapid component of the delayed rectifier potassium current, I_Kr, and the underlying hERG potassium channel are critical for the regulation of heart rhythm. Recent experimental studies revealed that hERG/I_Kr currents are modulated by - and -adrenergic stimulation, providing a pathophysiological explanation for the increased incidence of arrhythmias during stress. This review summarizes the current knowledge on hERG/I_Kr channel modulation by adrenergic activity. In addition, therapeutic approaches to future effective, more genotype-specific antiarrhythmic therapies are discussed.     

Rapid molecular characterization of Hb H disease in Chinese by polymerase chain reaction

Summary We have developed a rapid method to molecularly distinguish different types of Hb H disease. The study depended on (a) most of the Hb H disease in Taiwan having an-thalassemia-1 of the Southeast Asia type (-SEA) in one allele and (b) the differences of X box of-globin gene cluster in the other allele. To detect the -SEA allele, we utilized the primers located on either side of the breakpoint to do PCR, then characterized the amplified products. For the other allele, we sequenced part of the X box, and found that bases –2803 to –2461 of the X box of – ^3.7 belonged to the X box of ₂ globin gene. In – ^4.2, the bases belonged to the X box of ₁ globin gene, whereas in ^cs it contained both X boxes of ₁ and ₂ globin genes. There was anMboII site at this region of the X box of ₂ globin gene. We utilized PCR to amplify this region and digested it with restriction enzymeMboII, then combined it with another PCR of different primer pairs to molecularly diagnose different types of Hb H disease. One hundred and one cases of Hb H disease from different families were studied: all of the cases had one allele of -SEA deletion, while the other allele showed that 52/101 were – ^3.7, 41/101 were ^cs , 7/101 were – ^4.2, and 1/101 was – ^G.Taichung. Of 52 cases of Hb H with – ^3.7, 47 were type-I deletion and five were type-II deletion.     

Protection by nitecapone against sodium taurocholate-induced damage to cultured gastric cells

The goal of this study was to observe if nitecapone protected against taurocholate-induced damage in primary cultured rat gastric mucosal cells, as well as in a well-differentiated human gastric epithelial cell line (MKN 28). Prostaglandins were measured to analyze the protection mechanism. In primary rat gastric mucosal cell culture, nitecapone 125–250 M protected the cells significantly against damage induced by sodidum taurocholate, increasing cell viability by 31–38%. In the human gastric epithelial cell line, in which mitochondrial activity was measured as an indication of cell viability, nitecapone (62.5–250 M) protected the cells against sodium taurocholate-induced damage by 12–20%. Prostaglandin E₂, thromboxane B₂, and 6-keto-prostaglandin F₁ measurements in the primary cultured rat gastric mucosal cells showed that nitecapone (125 M and 250 M) significantly stimulated prostaglandin E₂ production (84.7% and 61.0%, respectively), and inhibited thromboxane B₂ formation (50% at 250 M), while the 6-keto-prostaglandin F₁ formation was unaffected. Nitecapone had no effect on prostaglandin E₂ production in the MKN 28 epithelial cell line. Indomethacin or aspirin, at concentrations that did not affect cell viability, antagonized the stimulative effect of nitecapone on prostaglandin E₂ formation in the primary cultured rat gastric mucosal cells. Although the prostaglandin E₂ synthesis was blocked, nitecapone still protected against cell damage induced by taurocholate. These results demonstrated the direct and efficacious protection of nitecapone on gastric cell level and suggest that the cytoprotection by nitecapone against taurocholate may not be mediated through the mechanism of stimulated synthesis of prostaglandin E₂.     

Plasma levels of human granulocytic elastase α1-proteinase inhibitor complex (E-α1-PI) in leukemia

Summary There is evidence that polymorphonuclear granulocytes release neutral proteinases such as elastase (E) and cathepsin G in the course of acute leukemia. These proteinases may inactivate clotting factors by unspecific degradation before they are eliminated via complex formation with endogenous inhibitors, e. g. the ₁-proteinase inhibitor (₁-PI). In this study it was attemped to correlate plasma levels of the E-₁-PI complex with factor XIII and antithrombin III in acute leukemia. Using a newly developed, sensitive enzyme-linked immunoassay the concentration of E-₁-PI in patients with various types of leukemia, malignant lymphoma or multiple myeloma was determined. Only patients with acute myelocytic or promyelocytic leukemia (AML, APL) and chronic myelocytic leukemia with and without blastic transformation (CML) showed moderate to high levels of E-₁-PI (2- to 20-fold of normal). However, coagulation factor concentration observed in the different types of leukemia seemed to be independent of elastase liberation. Most of the AML-patients with elevated E-₁-PI levels showed peroxidase positive blood cell smears.     

Analytical Performance of the New Coagulation Monitoring System INRatio™ for the Determination of INR Compared with the Coagulation Monitor Coaguchek® S and an Established Laboratory Method

An evaluation of the INRatio Prothrombin Time Monitoring system for determination of INR was done in two centers with a total of 5 healthy subjects and 77 subjects on oral anticoagulation. The INRatio and the Coaguchek® S were compared with an established laboratory method. The correlation coefficient of the comparison with the laboratory was r = 0.954 for INRatio and r = 0.937 for Coaguchek® S. The mean relative deviation from the lab method calculated according to Hill was 6.87% for INRatio, which is rated very goo, and 9.72% for Coaguchek® S (goo). The imprecision in the normal range (INR = 1.1) showed a coefficient of variation (CV) of 7.8% and a standard deviation (SD) of 0.09. In the therapeutic range (INR 3.9) the CV was 5.4%, the SD 0.21 and above therapeutic range (INR 5.3), the CV was 8.4% (SD 0.44), rated satisfactory. The concordances of the compared methods with the routine were 81% for INRatio and 79% for Coaguchek® S, which is considered state-of-the-art. Most of the patients perceptions of the INRatio were very positive.In the hands of professionals the INRatio demonstrated very good accuracy and precision and an excellent technical reliability. Further studies using INRatio for self testing by patients are warranted.     

Serum Levels of α1-Antitrypsin Predict Phenotypic Expression of the α1-Antitrypsin Gene

We conducted a retrospective analysis to determine if both ₁-antitrypsin serum level and phenotype need be studied when evaluating children for ₁-AT deficiency. We collected data from patients less than 19 years old who had both serum ₁-AT level and phenotype determined over a 9-year period (January 1992–December 2000). Eighty-eight patients were identified and 15 had the PiZZ phenotype. The serum ₁-AT level was below normal (normal 85–215 mg/dl) in all 15 PiZZ patients. Seventy-two of 73 non-PiZZ patients had normal or above normal serum levels. The sensitivity of the serum ₁-AT level was 100%, and the specificity was 99%. The serum ₁-AT level had a positive predictive value of 94% and a negative predictive value of 100%. We conclude that serum ₁-AT levels are highly predictive of the PiZZ phenotype. Determination of the serum ₁-AT level alone should be the initial test when evaluating for ₁-AT deficiency.     

Enzymatic determination of serum 3α-sulfated bile acids concentration with bile acid 3α-sulfate sulfohydrolase

A newly developed enzymatic method for determining urinary 3-sulfated bile acids was used to measure serum 3-sulfated bile acid levels in 114 patients with hepatobiliary diseases and 56 healthy subjects. The lowest measurable amount of the 3-sulfated bile acids was 0.5 µmol/liter. The standard curves for glycolithocholic acid 3-sulfate, glycoursodeoxycholic acid 3-sulfate, and lithocholic acid 3-sulfate were linear from 0.5 to 250 µmol/liter. Specificity of the assay was satisfactory and intra- and interassay variations ranged from 0.8 to 4.4% and from 1.2 to 7.9%, respectively. Analytical recovery was more than 91%. The values obtained by this assay were well correlated with those by gas-liquid chromatography measurement (r=0.91,P<0.01). The fasting serum 3-sulfated bile acids level in healthy subjects ranged from undetectable to 1.9 µmol/liter (mean±se; 0.9±0.1 µmol/liter). The percentage of 3-sulfated bile acids in total bile acids (sum of 3-sulfated and 3-hydroxy bile acids) in serum was 16.8±1.5%. In subjects with hepatobiliary diseases, serum 3-sulfated bile acids levels were elevated; however, the percentage of 3-sulfated bile acids in total bile acids was decreased and correlated with the severity of hepatocellular insufficiency. This enzymatic assay is simple, rapid, and accurate for the determination of serum 3-sulfated bile acids.     

Pharmacologic Characteristics of Rabbit Esophageal Muscularis Mucosae In Vitro

The aim of this study was to investigate invitro the pharmacologic properties of rabbit esophagealmuscularis mucosae. Stimulation of its motor innervationelicited only atropinesensitive excitatory responses. This tissue was not refractory to histamine butappeared to be rapidly desensitized to its effects.Responses to adrenoreceptor agonists were produced byexcitatory ₁ and ₁adrenoreceptors, inhibitory ₃ receptors but not₂ receptors. The esophageal muscularismucosae was only weakly stimulated by neurokinins andbradykinin, and these responses were mediated via NK2,NK3, B1, and B2 receptors, respectively. Adenosine diphosphate andadenosine triphosphate produced 40% maximalcontractions through the activation of P2 receptors,whereas adenosine monophosphate and adenosine werewithout effect. Responses to prostaglandins E₂ andF₂ were 10% of the tissues'maximum response to acetylcholine. These datademonstrate that rabbit esophageal muscularis mucosaehas a simple excitatory innervation and is only weaklystimulated by a variety of pharmacologic agents. For thesereasons it is distinct from muscularis mucosae foundelsewhere in the rabbit gastrointestinaltract.     

Expression and prognostic roles of integrins and interleukin-1 receptor type I in patients with ductal adenocarcinoma of the pancreas

To Investigate the prognostic indicator, we examined the expression of ₆- and ₅- integrin and interleukin-1 receptor type I (IL-1RI) immunohistochemically, and analyzed the correlation between immunohistochemical findings and clinicopathological factors in pancreatic cancer. In patients with a strongly expressing ₆- integrin subunit or weakly expressing ₅₁-integrin in pancreatic cancer tissues there was a significant association with advanced TNM stage (P = 0.027 and 0.014, respectively), presence of liver metastases (P = 0.032 and 0.002, respectively), and poor prognosis (P = 0.0155 and 0.0056, respectively). In patients with a weakly expressing ₆ integrin subunit or weakly expressing ₅₁-integrin in noncancerous pancreatic tissues there was a significant association with poor prognosis (P = 0.0324 and 0.0396, respectively). Multivariate analysis demonstrated that strong expression of ₆- and weak expression of ₅₁-integrin were found to be independent prognosticators in pancreatic cancer patients. Our present results indicate that ₆₁- and ₅₁-integrin expression can be a significant prognostic indicator in pancreatic cancer.     

Human Plasma Fibronectin Mediates Adhesion of U937 Cells by RGD and CS1

Fibronectin specifically binds to U937 cells (monocytic cell line) in a dose-dependent manner. The specific receptors for the RGD sequence have been identified as ₅₁ and _IIb3, and that for CS1 has been defined as ₄₁. RGDS, CS1 peptide, and two peptides together showed similar inhibitory activities on this adhesion, while the 29-kD dispase-digested fragment of the C-terminal heparin-binding domain did not. Thus, the adhesion of fibronectin to U937 cells is mainly mediated by RGDS in the cell-binding domain and CS1 in the alternatively spliced region. Flow cytometry using monoclonal antibodies revealed expressions of ₃₁, ₄₁, and ₅₁, and not expression of ₂₁. Adhesion of U937 cells to fibronectin-coated wells is specific and is inhibited by anti-₄₁ and anti- ₅₁ monoclonal antibodies. The IC-50 for anti-₅₁ antibody was almost a log lower than the value for anti-₄₁ antibody. These results demonstrated that interactions of RGDS and CS1 sequence of fibronectin with ₅₁ and ₄₁ on U937 cells were required for the adhesion of U937 cells to fibronectin. These results may provide further information to understand the mechanism(s) of tumor cell adhesion and atherogenesis.     

Interleukin-2-activated killer cell activity in colorectal tumor patients: evaluation of in vitro effects by prothymosinα1

The effects of prothymosin 1 (Pro 1) in combination with interleukin-2 (IL-2) on peripheral blood lymphocytes from 50 colorectal tumor patients at different stages were studied with respect to immunocytotoxicity, adhesion to cultured SW620 colon carcinoma cells, secretion of cytokines and expression of adhesion and surface marker molecules. On average, the patients showed lower natural killer (NK) cell activity than healthy donors, which was associated with a lower adhesion capacity to the tumor target cells. The NK cell activity of the patients was inversely related to the tumor stage. The generation of lymphokine(IL-2)-activated killer (LAK) cell activity was found to be comparable on lymphocytes from healthy individuals and patients and was not correlated to tumor stage. Pro 1 stimulated patients' LAK cell activity only, primarily at the early stage (Dukes A/B). The Pro 1 effect was associated with an increased adhesion of lymphocytes to tumor target cells and an increased secretion of the deficient IL-2-induced IFN secretion. No significant effects on the low level of TNF secretion was noted. By flow cytometry, Pro 1 in combination with IL-2 augmented the expression of the NK cell markers CD56, CD16/56, the subset CD3/16/56 and CD25 on lymphocytes of the patients. In contrast, Pro 1 was equally effective by increasing the expression of CD18 and CD11a, on lymphocytes from the patients and from normal controls. In conclusion, Pro 1, in combination with IL-2, can partially normalize lymphocyte deficiencies of colon cancer patients in vitro. This potential might provide an experimental basis for applying Pro 1 or related thymic peptides in selected immunotherapies against colorectal tumors.Abbreviations Pro 1 prothymosin 1 - NK natural killer - LAK lymphokine-activated killer - IL-2 interleukin-2 - TNF tumor necrosis factor - IFN interferon - PBL peripheral blood lymphocytes - ELISA enzyme-linked immunosorbent assay     

Regulation of the release of tumour necrosis factor (TNF)α and soluble TNF Receptor by γ irradiation and interferon γ in Ewing's sarcoma/peripheral primitive neuroectodermal tumour cells

This study analyses the production of tumour necrosis factor (TNF) and soluble TNF receptor (sTNF-R) before and after exposure to irradiation and interferon (IFN) in 12 cell lines derived from Ewing's sarcoma (ES)/peripheral primitive neuroectodermal tumours (pPNET). Supernatants from ES/pPNET cell cultures were tested in a TNF-specific amplified enzyme-linked immunosorbent assay (ELISA), a bioassay, and sTNF-R_p55 and sTNF-R_p75 ELISA. The tumour cell lines released minimal amounts of TNF, prominent amounts of sTNF-R_p55 (7/12 cell lines) and no sTNF-R_p75. Exposure to irradiation (5 Gy) either induced (3/12) cell lines) or up-regulated (3/12 cell lines) TNF release without changing sTNF-R_p55 and sTNF-R_p75 levels. Priming of cultures with recombinant human IFN (rhIFN) markedly enhanced TNF secretion in the radiation-responsive cell lines and had no influence on sTNF-R_p55 and sTNF-R_p75 levels. rhIFN affected the magnitude rather than the sensitivity of the radiation response. The TNF secreted was bioactive, as shown by its cytotoxic effect of WEHI-164 cells, and neutralization of its activity by anti-TNF monoclonal antibody. Herbimycin A (a tyrosine-specific protein kinase inhibitor) but not calphostin C (a protein kinase C inhibitor), H89 (a protein kinase A inhibitor), AACOCF3 (a specific inhibitor of phospholipase A₂) and MK-886 (a specific inhibitor of 5-lipoxygenase) abrogated -irradiation-stimulated TNF release. The antioxidantsN-acetylcysteine, nordihydroguaiaretic acid and mepacrine dose-dependently inhibited -irradiation-mediated TNF production. Collectively our findings indicate that IFN priming potentiates the secretion of bioactive TNF by ES/pPNET cells in response to irradiation without affecting sTNF-R release. The data suggest a requirement for protein tyrosine kinase activity and a role for reactive oxygen species in the -irradiation-mediated intracellular signalling pathway leading to TNF production.     

Heat shock protein induction in rat pancreatic islets by recombinant human interleukin 1β

Summary Interleukin 1, potentiated by tumour necrosis factor , is cytotoxic to pancreatic Beta cells in vitro. We have hypothesized that interleukin 1 induces oxygen free radicals in Beta cells. Since cytotoxicity induced by free radicals and by heat may activate the same cellular repair mechanism (the heat shock response), the aim of this study was to investigate the pattern of protein synthesis in isolated islets after exposure to interleukin 1 (150 pg/ml, 24 h), tumour necrosis factor (50 ng/ml, 24 h), heat shock (43°C, 30 min) and H₂O₂ (0.1 mmol/l, 20 min). By polyacrylamide gel electrophoresis, autoradiography, Western-blot analysis and partial peptide mapping of ³⁵S-methionine labelled islets, interleukin 1 was found to induce a 73 kilodalton protein belonging to the heat shock protein family heat shock protein 70, a heat shock protein 90, and haem oxygenase. A minor induction of heat shock protein 73 and haem oxygenase was seen after H₂O₂. Interleukin 1 did not induce heat shock proteins in rat thyroid cells, rat mesangial cells or in human monocytes. Tumour necrosis factor did not induce selective protein synthesis. Pre-exposure of islets to heat, tumour necrosis factor , or H₂O₂ did not prevent the impairment of glucose-stimulated insulin release seen after 24 h of interleukin 1 exposure. The data are compatible with free radical induction by interleukin 1. However, the heat shock response is not specific for oxidative injury, and previous studies have shown discrepant effects as to a protective effect of free radical scavengers against interleukin 1-mediated beta-cytotoxicity. Thus, a role for free radicals in this context is not definitely proven.