Gradual cold acclimation induces cardioprotection without affecting ß-adrenergic receptor-mediated adenylyl cyclase signaling.

Novel strategies are needed that can stimulate endogenous signaling pathways to protect the heart from myocardial infarction. The present study tested the hypothesis that appropriate regimen of cold acclimation (CA) may provide a promising approach for improving myocardial resistance to ischemia/reperfusion (I/R) injury without negative side effects. We evaluated myocardial I/R injury, mitochondrial swelling, and ß-adrenergic receptor (ß-AR)-adenylyl cyclase-mediated signaling. Male Wistar rats were exposed to CA (8°C, 8 h/day for a week, followed by 4 wk at 8°C for 24 h/day), while the recovery group (CAR) was kept at 24°C for an additional 2 wk. The myocardial infarction induced by coronary occlusion for 20 min followed by 3-h reperfusion was reduced from 56% in controls to 30% and 23% after CA and CAR, respectively. In line, the rate of mitochondrial swelling at 200 µM Ca2+ was decreased in both groups. Acute administration of metoprolol decreased infarction in control group and did not affect the CA-elicited cardiprotection. Accordingly, neither ß1-AR-Gsα-adenylyl cyclase signaling, stimulated with specific ligands, nor p-PKA/PKA ratios were affected after CA or CAR. Importantly, Western blot and immunofluorescence analyses revealed ß2- and ß3-AR protein enrichment in membranes in both experimental groups. We conclude that gradual cold acclimation results in a persisting increase of myocardial resistance to I/R injury without hypertension and hypertrophy. The cardioprotective phenotype is associated with unaltered adenylyl cyclase signaling and increased mitochondrial resistance to Ca2+-overload. The potential role of upregulated ß2/ß3-AR pathways remains to be elucidated.NEW & NOTEWORTHY We present a new model of mild gradual cold acclimation increasing tolerance to myocardial ischemia/reperfusion injury without hypertension and hypertrophy. Cardioprotective phenotype is accompanied by unaltered adenylyl cyclase signaling and increased mitochondrial resistance to Ca2+-overload. The potential role of upregulated ß2/ß3-adrenoreceptor activation is considered. These findings may stimulate the development of novel preventive and therapeutic strategies against myocardial ischemia/reperfusion injury.

[Comparison of immunochemical and biochemical tests for occult hemorrhage in feces]. / Srovnání imunochemického a biochemického testu okultního krvácení ve stolici.

The authors compared in a group of 104 patients assessment of occult haemorrhage in faeces made by the immunochemical test HemeSelect (HS-SmithKline Diagnostics) and the biochemical Haemoccult test (HT-Röhm Pharma). In all patients subsequently total coloscopy was performed. In the whole group the sensitivity of HS was 49.3% and of HT 16.0% (p << 0.001) and the specificity 72.4% and 100% (p << 0.01). The predictive value in polyps, 10 mm in size or larger, was 65.2% (positive) and 60.0% (negative). The assessed sensitivity and predictive values of HS do not permit to recommend immunochemical tests of this type as an alternative procedure to repeated colonoscopic checks in the dispensarization of high risk groups of colorectal cancer.