Evaluation of cardiac troponin I stability in blood sample using the AccuTnI+3 assay

OBJECTIVE

Troponins are considered as the biomarkers of choice to highlight cardiac injury in emergency departments, but are also valuable to detect cardiac injury in a non-emergency setting. In this latter case, transport of blood samples to laboratories often exceeds the manufacturer's recommendations (<2 h between vein puncture and analysis for the Beckman Coulter AccuTnI+3 assay). We aim to evaluate in vitro the stability of troponin Ic (cTnI) at two intervals (<2 h and at 4 h) over a wide range of concentrations using the Beckman Coulter AccuTnI+3 assay.

PATIENTS AND METHODS

For each of the 95 patients included in this study, we analyzed the first blood sample with a time of transport <2 h, and the second sample after 4 h from vein puncture. We then calculated the correlation between the two periods of analysis and evaluated the bias by a Bland-Altman test.

RESULTS

Taking into account of our analytical reproducibility, we did not observe any significant differences in cTnI values between <2 h and 4 h.

CONCLUSIONS

The time between vein puncture and analysis of cTnI can be extended to 4 h.

Effects of glycaemic variability on cardiac remodelling after reperfused myocardial infarction: Evaluation of streptozotocin-induced diabetic Wistar rats using cardiac magnetic resonance imaging

AIMS

In addition to hyperglycaemia, glycaemic variability seems to be associated with poor outcomes after acute myocardial infarction. This study explored the impact of glycaemic variability in diabetic Wistar rats subjected to myocardial ischaemia/reperfusion.

METHODS

Animals with streptozotocin-induced diabetes received insulin either to maintain stable hyperglycaemia (Dh group) or to generate glycaemic variability (Dv). After experimental myocardial ischaemia/reperfusion was surgically induced, 7T cardiac magnetic resonance imaging (CMR) was performed at weeks 1 (w1) and 3 (w3).

RESULTS

Twenty-six rats were randomized [sham group (S): n=5; control group (C): n=7; Dh group: n=6; and Dv group: n=8]. The mean amplitude of glucose reflecting glycaemic variability was higher in the Dv than in the Dh group (9.1±2.7mmol/L vs 5.9±1.9mmol/L; P<0.05). CMR assessment at w3 revealed ventricular enlargement in both Dh and Dv groups compared with the C and S groups (end-diastolic volume: 1.60±0.22 and 1.36±0.30mL/kg compared with 1.11±0.13 and 0.87±0.11mL/kg, respectively; P<0.05). Circumferential strain was altered between w1 and w3 in the remote area only in the Dv group, resulting in a lower value in this group than in the S, C and Dh groups (-0.11±0.01 vs -0.17±0.05, -0.15±0.03 and -0.16±0.03, respectively; P<0.05). In addition, at w3, oedema was also higher in the remote area in the Dv than in the C group (18.3±4.9ms vs 14.5±1.7ms, respectively; P<0.05).

CONCLUSION

In the context of experimental myocardial ischaemia/reperfusion, our results suggest that glycaemic variability might have a potentially deleterious impact on myocardial outcomes beyond the classical glucose metrics.

Remifentanil produces cross-desensitization and tolerance with morphine on the mu-opioid receptor

Remifentanil is a powerful mu-opioid (MOP) receptor agonist used in anaesthesia with a very short half-life. However, per-operative perfusion of remifentanil was shown to increase morphine consumption during post-operative period to relieve pain. In the present study, we aimed to describe the cellular mechanisms responsible for this apparent reduction of morphine efficacy. For this purpose, we first examined the pharmacological properties of both remifentanil and morphine at the MOP receptor, endogenously expressed in the human neuroblastoma SH-SY5Y cell line, to regulate adenylyl cyclase and the MAP kinase ERK1/2 pathway, their potency to promote MOP receptor phosphorylation, arrestin 3-CFP (cyan fluorescent protein) recruitment and receptor trafficking during acute and sustained exposure. In the second part of this work, we studied the effects of a prior exposure of remifentanil on morphine-induced inhibition of cAMP accumulation, activation of ERK1/2 and analgesia. We showed that sustained exposure to remifentanil promoted a rapid desensitization of opioid receptors on both signalling pathways and a pretreatment with this agonist reduced signal transduction produced by a second challenge with morphine. While both opioid agonists promoted Ser(375) phosphorylation on MOP receptor, remifentanil induced a rapid internalization of opioid receptors compared to morphine but without detectable arrestin 3-CFP translocation to the plasma membrane in our experimental conditions. Lastly, a cross-tolerance between remifentanil and morphine was observed in mice using the hot plate test. Our in vitro and in vivo data thus demonstrated that remifentanil produced a rapid desensitization and internalization of the MOP receptor that would reduce the anti-nociceptive effects of morphine.