Gut microbiome alterations in type 1 autoimmune pancreatitis after induction of remission by prednisolone.

Although increasing evidence demonstrates the association between intestinal dysbiosis and pancreatic diseases such as chronic pancreatitis and pancreatic cancer, it remains largely unknown whether intestinal dysbiosis is involved in the immunopathogenesis of autoimmune pancreatitis (AIP). Recently, we found that intestinal dysbiosis mediates experimental AIP via the activation of plasmacytoid dendritic cells (pDCs), which can produce interferon (IFN)-α and interleukin (IL)-33. However, candidate intestinal bacteria, which promote the development of AIP, have not been identified. Fecal samples were obtained from type 1 AIP patients before and after prednisolone (PSL) treatment and subjected to 16S ribosomal RNA sequencing to evaluate the composition of intestinal bacteria. Induction of remission by PSL was associated with the complete disappearance of Klebsiella species from feces in two of the three analyzed patients with type 1 AIP. To assess the pathogenicity of Klebsiella species, mild experimental AIP was induced in MRL/MpJ mice by repeated injections of 10 µg of polyinosinic-polycytidylic acid [poly(I:C)], in combination with oral administration of heat-killed Klebsiella pneumoniae. The AIP pathology score was significantly higher in MRL/MpJ mice that received both oral administration of heat-killed K. pneumoniae and intraperitoneal injections of poly(I:C) than in those administered either agent alone. Pancreatic accumulation of pDCs capable of producing large amounts of IFN-α and IL-33 was also significantly higher in mice that received both treatments. These data suggest that intestinal colonization by K. pneumoniae may play an intensifying role in the development of type 1 AIP.

Combination gemcitabine plus S-1 versus gemcitabine plus cisplatin for advanced/recurrent biliary tract cancer: the FUGA-BT (JCOG1113) randomized phase III clinical trial.

BACKGROUND: Gemcitabine plus cisplatin (GC) is the standard treatment of advanced biliary tract cancer (BTC); however, it causes nausea, vomiting, and anorexia, and requires hydration. Gemcitabine plus S-1 (GS) reportedly has equal to, or better, efficacy and an acceptable toxicity profile. We aimed to confirm the non-inferiority of GS to GC for patients with advanced/recurrent BTC in terms of overall survival (OS). PATIENTS AND METHODS: We undertook a phase III randomized trial in 33 institutions in Japan. Eligibility criteria included chemotherapy-naïve patients with recurrent or unresectable BTC, an Eastern Cooperative Oncology Group Performance Status of 0 - 1, and adequate organ function. The calculated sample size was 350 with a one-sided α of 5%, a power of 80%, and non-inferiority margin hazard ratio (HR) of 1.155. The primary end point was OS, while the secondary end points included progression-free survival (PFS), response rate (RR), adverse events (AEs), and clinically significant AEs defined as grade ≥2 fatigue, anorexia, nausea, vomiting, oral mucositis, or diarrhea. RESULTS: Between May 2013 and March 2016, 354 patients were enrolled. GS was found to be non-inferior to GC [median OS: 13.4 months with GC and 15.1 months with GS, HR, 0.945; 90% confidence interval (CI), 0.78-1.15; P = 0.046 for non-inferiority]. The median PFS was 5.8 months with GC and 6.8 months with GS (HR 0.86; 95% CI 0.70-1.07). The RR was 32.4% with GC and 29.8% with GS. Both treatments were generally well-tolerated. Clinically significant AEs were observed in 35.1% of patients in the GC arm and 29.9% in the GS arm. CONCLUSIONS: GS, which does not require hydration, should be considered a new, convenient standard of care option for patients with advanced/recurrent BTC. CLINICAL TRIAL NUMBER: This trial has been registered with the UMIN Clinical Trials Registry (http://www.umin.ac.jp/ctr/index.htm), number UMIN000010667.

Comparison of Bispectral Index and Entropy values with electroencephalogram during surgical anaesthesia with sevoflurane.

BACKGROUND: Concomitantly recorded Bispectral Index® (BIS) and Entropy™ values sometimes show discordant trends during general anaesthesia. Previously, no attempt had been made to discover which EEG characteristics cause discrepancies between BIS and Entropy. We compared BIS and Entropy values, and analysed the changes in the raw EEG signal during surgical anaesthesia with sevoflurane. METHODS: In this prospective, open-label study, 65 patients receiving general anaesthesia with sevoflurane were enrolled. BIS, Entropy and multichannel digital EEG were recorded. Concurrent BIS and State Entropy (SE) values were selected. Whenever BIS and SE values showed ≥10-unit disagreement for ≥60 s, the raw EEG signal was analysed both in time and frequency domain. RESULTS: A ≥10-unit disagreement ≥60 s was detected 428 times in 51 patients. These 428 episodes accounted for 5158 (11%) out of 45 918 analysed index pairs. During EEG burst suppression, SE was higher than BIS in 35 out of 49 episodes. During delta-theta dominance, BIS was higher than SE in 141 out of 157 episodes. During alpha or beta activity, SE was higher than BIS in all 49 episodes. During electrocautery, both BIS and SE changed, sometimes in the opposite direction, but returned to baseline values after electrocautery. Electromyography caused index disagreement four times (BIS > SE). CONCLUSIONS: Certain specific EEG patterns, and artifacts, are associated with discrepancies between BIS and SE. Time and frequency domain analyses of the original EEG improve the interpretation of studies involving BIS, Entropy and other EEG-based indices. CLINICAL TRIAL REGISTRATIONCLINICALTRIALSGOVIDENTIFIER: NCT01077674.

Suppressed G-protein-coupled receptor kinase 2 activity protects female diabetic-mouse aorta against endothelial dysfunction.

AIM: Pre-menopausal women have less cardiovascular disease and lower cardiovascular morbidity and mortality than men the same age. Previously, we noted in mice that G-protein-coupled receptor kinase 2 (GRK2) negatively regulates the Akt/eNOS pathway in male diabetic aortas and that endothelial function via the Akt/eNOS pathway is less affected in female diabetic aortas. The cellular mechanisms underlying these sex differences remain unclear. We aimed to investigate the ways in which GRK2 might modulate vascular functions in male and female diabetic mice (DM). METHODS: Vascular functions were examined in aortic rings. GRK2, ß-arrestin 2 and Akt/eNOS-signalling-pathway protein levels and activities were assayed by Western blotting. RESULTS: Phenylephrine-induced contraction was greater, while both clonidine-induced and insulin-induced relaxations were weaker (vs. male controls), in aortas from male type 2 DM, suggesting impairments of the Akt/eNOS pathway and α-adrenoceptor function. GRK2-inhibitor reversed only the impairment in Akt/eNOS-pathway-mediated relaxation in male DM. Increases in GRK2 activity, GRK2 expression in the membrane, plasma Ang II and systolic blood pressure were seen in male DM (vs. male controls) but not in female DM; these increases were attenuated by GRK2-inhibitor treatment. Repeatedly obtaining clonidine concentration-response curves led to reduced relaxation in male and in female DM aortas, indicating similar desensitization between female DM and male DM. This effect was reversed by GRK2-inhibitor in both sexes. CONCLUSION: GRK2 plays a key role in modulating the aortic vasodilator effect of clonidine by selectively affecting the Akt/eNOS pathway. This action of GRK2 is more powerful in male than in female DM.

Can electromyographic arousal be detected visually on the Datex-Ohmeda S/5™ anesthesia monitor?

BACKGROUND: Electroencephalogram (EEG)-based depth of anaesthesia monitoring is susceptible to contaminating electromyographic (EMG) activity. Many authorities have suggested that anaesthesiologists using these monitors should interpret the raw EEG waveform seen on the anaesthesia monitor. METHODS: In 34 patients anaesthetized with propofol using two doses of rocuronium (0.6 and 1.2 mg/kg), we studied whether the EMG arousal can be detected visually on the anaesthesia monitor. The Bispectral Index (BIS) and Entropy biosignals on the monitor were recorded with a video camera, and the one-channel EEG recorded by the Entropy strip was collected on a laptop computer. The recordings and the one-channel EEG were analyzed offline by two experts (anaesthesiologist and neurophysiologist), both with a long experience on anaesthesia-related EEG. RESULTS: EMG arousal existed in 14/34 and 13/33 patients in the BIS and Entropy biosignals, respectively. The anaesthesiologist detected EMG on the monitor in 7/14 patients with BIS (sensitivity 50%) and in 4/13 patients with Entropy (31%). The clinical neurophysiologist detected EMG in 6/14 (43%) patients with BIS and in 5/13 (38%) with Entropy. The specificity of the EMG analyses was 55 and 65% with BIS, and 85 and 90% with Entropy. EMG arousal was detected in BIS biosignal in 10/17 and 4/17 patients with 0.6 and 1.2 mg/kg doses of rocuronium (P = 0.04). CONCLUSIONS: In contrast to many EEG phenomena, EMG activity cannot be accurately detected visually from the raw EEG on the anaesthesia monitor. Further development in the quality of the anaesthesia monitors is warranted.

Mechanisms underlying reduced P2Y(1) -receptor-mediated relaxation in superior mesenteric arteries from long-term streptozotocin-induced diabetic rats.

AIM: Extracellular nucleotides activate cell-surface purinergic (P2) receptors, contribute to the local regulation of vascular tone and play important roles in pathophysiological states. However, little is known about the vasodilator effects of P2Y(1) -receptor activation in diabetic states. We hypothesized that in a model of established type 1 diabetes, long-term streptozotocin (STZ)-induced diabetic rats, the arterial relaxation elicited by a P2Y(1) -receptor agonist would be impaired. METHODS: Relaxations to adenosine 5'-diphosphate sodium salt (ADP), 2-MeSADP (selective P2Y(1) -receptor agonist) and adenosine 5'-triphosphate disodium salt (ATP) were examined in superior mesenteric artery rings from long-term STZ-induced diabetic rats (at 50-57 weeks after STZ injection). ADP-stimulated nitric oxide (NO) production in the superior mesenteric artery was assessed by measuring the levels of NO metabolites. Mesenteric artery expressions of P2Y(1) receptor, and ADP-stimulated levels of phosphorylated endothelial NO synthase (eNOS) (at Ser(1177) and at Thr(495) ) and eNOS were detected by Western blotting. RESULTS: Arteries from diabetic rats exhibited (vs. those from age-matched control rats): (i) reduced ADP-induced relaxation, which was partly or completely inhibited by endothelial denudation, by NOS inhibitor treatment and by a selective P2Y(1) -receptor antagonist, (ii) reduced 2-MeSADP-induced relaxation, (iii) reduced ADP-stimulated release of NO metabolites and (iv) impaired ADP-induced stimulation of eNOS activity (as evidenced by reduced the fold increase in eNOS phosphorylation at Ser(1177) with no difference in fold increase in eNOS phosphorylation at Thr(495) ). The protein expression of P2Y(1) receptor did not differ between diabetic and control arteries. CONCLUSIONS: These results suggest that P2Y(1) -receptor-mediated vasodilatation is impaired in superior mesenteric arteries from long-term type 1 diabetic rats. This impairment is because of reduced P2Y(1) -receptor-mediated NO signalling, rather than to reduced P2Y(1) -receptor expression.

Elevated BIS and Entropy values after sugammadex or neostigmine: an electroencephalographic or electromyographic phenomenon?

BACKGROUND: Sugammadex is designed to antagonize neuromuscular blockade (NMB) induced by rocuronium or vecuronium. In clinical practice, we have noticed a rise in the numerical values of bispectral index (BIS) and Entropy, two electroencephalogram (EEG) - based depth of anesthesia monitors, during the reversal of the NMB with sugammadex. The aim of this prospective, randomized, double-blind study was to test this impression and to compare the effects of sugammadex and neostigmine on the BIS and Entropy values during the reversal of the NMB. METHODS: Thirty patients undergoing gynecological operations were studied. Patients were anesthetized with target-controlled infusions of propofol and remifentanil, and rocuronium was used to induce NMB. After operation, during light propofol-remifentanil anesthesia, NMB was antagonized with sugammadex or neostigmine. During the following 5 min, the numerical values of BIS, BIS electromyographic (BIS EMG) and Entropy were recorded on a laptop computer, as well as the biosignal recorded by the Entropy strip. The Entropy biosignal was studied off-line both in time and frequency domain to see if NMB reversal causes changes in EEG. RESULTS: In some patients, administration of sugammadex or neostigmine caused a significant rise in the numerical values of BIS, BIS EMG and Entropy. This phenomenon was most likely caused by increased electromyographic (EMG) activity. The administration of sugammadex or neostigmine appeared to have only minimal effect on EEG. CONCLUSION: The EMG contamination of EEG causes BIS and Entropy values to rise during reversal of rocuronium-induced NMB in light propofol-remifentanil anesthesia.

Pravastatin normalizes endothelium-derived contracting factor-mediated response via suppression of Rho-kinase signalling in mesenteric artery from aged type 2 diabetic rat.

AIM: Although pravastatin has known pleiotropic effects against adverse cardiovascular conditions, little is known about its effects on endothelium-derived contracting factor (EDCF)-mediated signalling. We aimed to determine the effects of pravastatin on the production of and responses to EDCF in superior mesenteric arteries isolated from rats at the chronic stage of type 2 diabetes. METHODS: Contractions to acetylcholine (ACh) were examined in superior mesenteric artery rings from aged type 2 diabetic Otsuka Long-Evans Tokushima Fatty (OLETF) rats (56-60 weeks old), from control age-matched non-diabetic Long-Evans Tokushima Otsuka (LETO) rats and from pravastatin-treated (10 mg kg(-1) , p.o., daily for 4 weeks) OLETF rats. Mesenteric artery expressions of cyclo-oxygenases (COXs), microsomal-PGE synthases (mPGESs), RhoA and Rho-kinase proteins, and also the level of phosphorylated ezrin, radixin and moesin (PERM), a substrate for Rho-kinase, were detected by Western blotting. RESULTS: Arteries from OLETF rats exhibited (vs. LETO rats) (1) enhanced ACh-induced EDCF-mediated contractions, which were inhibited by the Rho-kinase inhibitor Y27632, (2) reductions in the ACh-stimulated release of both PGE(2) and superoxide and (3) increased COX-1 and PERM protein expressions. Mesenteric arteries from OLETF rats treated with pravastatin exhibited (vs. untreated OLETF) (1) reduced ACh-induced contraction, (2) suppressed ACh-induced PGE(2) production and superoxide generation and (3) reduced ACh-induced PERM protein expression. CONCLUSIONS: These results suggest that pravastatin exerts beneficial effects against abnormal EDCF signalling by suppressing Rho-kinase and promoting antioxidant activity in the mesenteric arteries of rats at the chronic stage of type 2 diabetes.

Explaining Entropy responses after a noxious stimulus, with or without neuromuscular blocking agents, by means of the raw electroencephalographic and electromyographic characteristics.

BACKGROUND: Entropy™, an anaesthetic EEG monitoring method, yields two parameters: State Entropy (SE) and Response Entropy (RE). SE reflects the hypnotic level of the patient. RE covers also the EMG-dominant part of the frequency spectrum, reflecting the upper facial EMG response to noxious stimulation. We studied the EEG, EMG, and Entropy values before and after skin incision, and the effect of rocuronium on Entropy and EMG at skin incision during sevoflurane-nitrous oxide (N2O) anaesthesia. METHODS: Thirty-eight patients were anaesthetized with sevoflurane-N2O or sevoflurane-N2O-rocuronium. The biosignal was stored and analysed off-line to detect EEG patterns, EMG, and artifacts. The signal, its power spectrum, SE, RE, and RE-SE values were analysed before and after skin incision. The EEG arousal was classified as ß (increase in over 8 Hz activity and decrease in under 4 Hz activity with a typical ß pattern) or δ (increase in under 4 Hz activity with the characteristic rhythmic δ pattern and a decrease in over 8 Hz activity). RESULTS: The EEG arousal appeared in 17 of 19 and 15 of 19 patients (NS), and the EMG arousal in 0 of 19 and 13 of 19 patients (P<0.01) with and without rocuronium, respectively. Both ß (n=30) and EMG arousals increased SE and RE. The δ arousal (n=2) decreased both SE and RE. A significant increase in RE-SE values was only seen in patients without rocuronium. CONCLUSIONS: During sevoflurane-N2O anaesthesia, both EEG and EMG arousals were seen. ß and δ arousals had opposite effects on the Entropy values. The EMG arousal was abolished by rocuronium at the train of four level 0/4.

A comparison of the Airway Scope and McCoy laryngoscope in patients with simulated restricted neck mobility.

We compared the efficacy of the Airway Scope and McCoy laryngoscope as intubation tools with the neck stabilised by a rigid cervical collar. After induction of anaesthesia and neck stabilisation, 100 patients were randomly assigned to tracheal intubation with an Airway Scope or McCoy laryngoscope. Overall intubation success rate, time required for intubation, number of intubation attempts required for successful intubation, and airway complications related to intubation were recorded. Overall intubation success rates were 100% with both devices and a similar number of intubation attempts were required. However, the mean (SD) time required for successful intubation was shorter with the Airway Scope (30 (7) s) than with the McCoy laryngoscope (40 (14) s; p < 0.0001). The incidences of intubation complications were similar, but oesophageal intubation (in six cases) occurred only with McCoy laryngoscope.

Diabetic state, high plasma insulin and angiotensin II combine to augment endothelin-1-induced vasoconstriction via ETA receptors and ERK.

BACKGROUND AND PURPOSE: Mechanisms associated with the enhanced contractile response to endothelin-1 in hyperinsulinaemic diabetes have been examined using the rat aorta. Functions for angiotensin II, endothelin-1 receptor expression and extracellular signal-regulated kinase (ERK) have been investigated. EXPERIMENTAL APPROACH: Streptozotocin-induced diabetic rats were infused with angiotensin II or, following insulin treatment, were treated with losartan, an angiotensin II receptor antagonist. Contractions of aortic strips with or without endothelium, in response to endothelin-1 and angiotensin II, were examined in vitro. Aortic ET(A) receptors and ERK/MEK expression were measured by western blotting. KEY RESULTS: Insulin-treated diabetic rats exhibited increases in plasma insulin, angiotensin II and endothelin-1. The systolic blood pressure and endothelin-1-induced contractile responses in aortae in vitro were enhanced in insulin-treated diabetic rats and blunted by chronic losartan administration. LY294002 (phosphatidylinositol 3-kinase inhibitor) and/or PD98059 (MEK inhibitor) diminished the enhanced contractile response to endothelin-1 in aortae from insulin-treated diabetic rats. ET(A) and ET(B) receptors, ERK-1/2 and MEK-1/2 protein expression and endothelin-1-stimulated ERK phosphorylation were all increased in aortae from insulin-treated diabetic rats. Such increases were blunted by chronic losartan administration. Endothelin-1-induced contraction was significantly higher in aortae from angiotensin II-infused diabetic rats. angiotensin II-infusion increased ERK phosphorylation, but the expression of endothelin receptors and ERK/MEK proteins remained unchanged. CONCLUSIONS AND IMPLICATIONS: These results suggest that the combination of high plasma angiotensin II and insulin with a diabetic state induced enhancement of endothelin-1-induced vasoconstriction, ET(A) receptor expression and ERK expression/activity in the aorta. Losartan improved both the diabetes-related abnormalities and the diabetic hypertension.

Airway scope and gum elastic bougie with Macintosh laryngoscope for tracheal intubation in patients with simulated restricted neck mobility.

BACKGROUND: /st> Airway Scope is a new videolaryngoscope which requires less cervical movement during intubation than direct laryngoscopy. Thus, in patients wearing a rigid cervical collar, we compared the efficacy of the Airway Scope and the gum elastic bougie with Macintosh laryngoscope during tracheal intubation. METHODS: /st> Anaesthesia was induced with propofol, fentanyl, and rocuronium. A rigid cervical collar was applied, and patients were randomly assigned to tracheal intubation with an Airway Scope (n=48) or multiple-use gum elastic bougie with Macintosh laryngoscope (n=48). Measurements included intubation time, gum elastic bougie insertion time, intubation success rate, and insertion and intubation attempts. Airway complications were also recorded. RESULTS: /st> The time required for successful intubation was significantly shorter with the Airway Scope compared with the gum elastic bougie with Macintosh laryngoscope [mean (sd) 34 (13) vs 49 (27) s, P=0.001], although the overall success rate of the Airway Scope (100%) compared with the gum elastic bougie with Macintosh laryngoscope (90%) did not reach the statistical significance (P=0.056). Oesophageal intubation (n=8) occurred only with the gum elastic bougie with Macintosh laryngoscope. Incidence of mucosal trauma and lip injury was similar with each device. No dental injury or hypoxia occurred with either device. CONCLUSIONS: /st> The Airway Scope shortens intubation time, is less likely to result in oesophageal intubation, and may offer a marginally higher intubation success rate in patients with simulated restricted neck mobility.

Involvement of TWEAK/Fn14 interaction in the synovial inflammation of RA.

OBJECTIVE: TWEAK, TNF-like weak inducer of apoptosis, induces not only apoptosis of some tumour cells, but also proliferation of endothelial cells, and angiogenesis. It is known that TWEAK induces production of cytokines that are involved in the pathogenesis of RA. However, it is not clear how TWEAK takes part in the synovitis of RA. In this study, we investigated the role of TWEAK/fibroblast growth factor-inducible 14 (Fn14) interaction in the synovitis of RA. METHODS: TWEAK and Fn14 expression on RA and OA synovial cells (SCs) were analysed by FACS. Synovial fibroblasts (SFs) or freshly isolated SCs were cultured in the presence or absence of recombinant TWEAK (rTWEAK) and anti-TWEAK or anti-Fn14 mAbs. Cell proliferation, cytokine/chemokine production and intercellular adhesion molecule (ICAM-1) expression were measured by WST-8 [2-(2-methoxy-4-nitrophenyl)-3-(4-nitrophenyl)-5-(2, 4-disulfophenyl)-2H-tetrazolium monosodium salt], ELISA and FACS, respectively. RESULTS: TWEAK expression was detected on CD45-positive population in RA synovium, whereas Fn14 was detected on both CD45-positive and CD45-negative populations. Cultured RA and OA SFs showed higher proliferation and produced IL-6, IL-8 and MCP-1 in response to rTWEAK. Cell proliferation and cytokine production of freshly isolated SCs from RA patients were suppressed by anti-TWEAK and anti-Fn14 mAbs. ICAM-1 expression on RA, but not OA, SFs was up-regulated by rTWEAK. CONCLUSIONS: These data suggest that TWEAK/Fn14 interaction plays a substantial role in the synovitis of RA, by directly inducing the proliferation of SFs, and by up-regulating the production of inflammatory cytokines/chemokines as well as the expression of ICAM-1.

Mechanisms underlying lysophosphatidylcholine-induced potentiation of vascular contractions in the Otsuka Long-Evans Tokushima Fatty (OLETF) rat aorta.

BACKGROUND AND PURPOSE: The effect of lysophosphatidylcholine (LPC) on aortic contractions in Otsuka Long-Evans Tokushima Fatty (OLETF) rats, a type 2 diabetic model, was studied. EXPERIMENTAL APPROACH: Using OLETF rats and control (Long Evans Tokushima Otsuka (LETO)) rats, the effects of LPC on the contractions induced by high-K(+) (10-40 mM), UK14,304 (10 approximately 100 nM; a selective alpha(2)-adrenoceptor agonist) and sodium orthovanadate (SOV; 10 microM approximately 3 mM) in endothelium-denuded aortae were compared. Aortic ERK activity and the mRNA expression for GPR4 (a putative LPC receptor) were also measured. KEY RESULTS: OLETF rats exhibited (vs. age-matched LETO rats): (1) greater potentiation of high-K(+)-induced contraction by 10 microM LPC - a potentiation attenuated by 10 microM genistein, protein tyrosine kinase (PTK) inhibitor, (2) greater potentiation of UK14,304 (10 approximately 100 nM)-induced contractions by LPC (1 microM approximately 10 microM) - a potentiation attenuated by 10 microM genistein, 50 microM tyrphostin A23 (PTK inhibitor) or 10 microM PD98059 (MEK 1/2 inhibitor), (3) greater basal and LPC (1 microM)-induced ERK activities, (4) greater basal and 100 nM UK14,304-stimulated ERK2 activities in both the absence and presence of 10 microM LPC, (5) greater SOV (10 microM approximately 3 mM)-induced contractions, (6) greater potentiation of SOV-induced contractions by 10 microM LPC - a potentiation suppressed by 10 microM PD98059 or 10 microM genistein, (7) upregulation of GPR4 mRNA. CONCLUSIONS AND IMPLICATIONS: These results suggest that the LPC-induced potentiation of contractions in the OLETF rat aorta may be attributable to increased PTKs or ERK activity and/or to receptor upregulation.

Enhancement of methoxamine-induced contractile responses of rat ventricular muscle in streptozotocin-induced diabetes is associated with alpha1A adrenoceptor upregulation.

AIM: To clarify the time-related changes in cardiac function and the mechanism underlying the cardiac dysfunction present in diabetes mellitus, we studied mechanical responses induced by alpha(1)- and beta-adrenoceptors, the Ca(2+)-entry promoter Bay K 8644- and ryanodine (an agent known to inhibit Ca(2+) release from the sarcoplasmic reticulum) in papillary muscles from streptozotocin (STZ)-induced diabetic and age-matched control rats. METHODS: Male Wistar rats received a single injection of STZ (60 mg kg(-1)) via the tail vein to induce diabetes. For the mechanical studies, papillary muscle preparations were suspended in an organ bath and isometric contractions were measured in 1-, 4-, and 10-week STZ-induced diabetic and age-matched control rats. RESULTS: In 1-week diabetic rats, the contractions induced by isoproterenol, methoxamine and Bay K 8644 were unchanged (vs. age-matched controls). In 4-week diabetic rats, (a) the isoproterenol- and Bay K 8644-induced contractions were impaired, (b) sensitivity to ryanodine was reduced, whereas (c) the methoxamine-induced contraction was unchanged. In 10-week diabetic rats, the isoproterenol- and Bay K 8644-induced contractile responses were impaired and the sensitivity to ryanodine was reduced, but in sharp contrast the methoxamine-induced contraction was enhanced. Both the mRNA level for the alpha(1A) adrenoceptor (but not the alpha(1B) or alpha(1D) mRNAs) and alpha(1A) adrenoceptor protein were increased in 10-week diabetic rats (vs. age-matched controls). CONCLUSION: These results suggest that impairments of beta-adrenergic and Ca(2+)-handling mechanisms occur early in the development of cardiomyopathy in STZ-induced diabetic rats, and that this is followed by augmentation of alpha(1A) adrenoceptor-mediated inotropy due to alpha(1A) adrenoceptor upregulation.