Circadian Variations in Blood Pressure, Heart Rate, and HR-BP Cross-Correlation Coefficient during Progression of Diabetes Mellitus in Rat

Alagebrium (ALT-711) improves the anti-hypertensive efficacy of nifedipine in diabetic-hypertensive rats

Combining drugs with complementary mechanisms of action may contribute to improved hypertension control in diabetic patients. Advanced glycation end-product (AGE) breakers, a new class of candidate drugs targeting aging-related cardiovascular dysfunction, may be useful as novel adjuvant agents to improve the efficacy of diabetic hypertension (DH) treatment. This study evaluated the effects of alagebrium (ALT-711), an AGE breaker, combined with nifedipine, a Ca(2+) channel blocker, in a rat model of streptozotocin-induced DH. Compared with monotherapy, combination treatment significantly decreased systolic and diastolic blood pressure values, increased the pulse pressure, and decreased the coefficient of variation of the systolic blood pressure. Plasma biochemistry indicated that the concentrations of prostacyclin and nitric oxide were increased. Gene expression analysis showed significantly decreased prepro-endothelin-1expression in the aorta. These results reveal that alagebrium significantly improves the anti-hypertensive actions of nifedipine in a rat model of DH and suggest its potential use in the successful control of clinical DH.

Measurement of right ventricular pressure by telemetry in conscious moving rabbits

Implantable radiotelemetry methodology has been used to continuously monitor pulmonary hemodynamics including right ventricular pressure (RVP) or pulmonary arterial pressure (PAP) in conscious, untethered and freely moving animals such as mice and rats. The use of implantable radiotelemetry to monitor RVP or PAP has never previously been described in rabbits. The aim of the present study was to use implantable radiotelemetry to continuously monitor RVP in conscious adult rabbits. Telemetry transmitters were implanted in 44 adult male New Zealand rabbits using a trans-diaphragm approach for the catheter placement. RVP, heart rate (HR) and activity were monitored every 15 min for 20 s. Body mass was recorded once a week. A total of 39 (88%) rabbits were successfully implanted. Thirty rabbits survived the surgical procedure resulting in an overall survival rate of 73%. RVP, HR and activity were long-term monitored in 17 rabbits for an average period of 103 ± 15 days. Weekly body mass follow-up showed that implantable radiotelemetry did not impair the normal development of the animal. Twenty-four-hour period monitoring of RVP, HR and activity showed concomitant changes in RVP, HR and activity according to the dark/light cycle applied to the rabbits. To conclude, implantable radiotelemetry methodology can be safely used to continuously monitor RVP in conscious rabbits.

An increase in the redox state during reperfusion contributes to the cardioprotective effect of GIK solution

This study aimed at determining whether glucose-insulin-potassium (GIK) solutions modify the NADH/NAD(+) ratio during postischemic reperfusion and whether their cardioprotective effect can be attributed to this change in part through reduction of the mitochondrial reactive oxygen species (ROS) production. The hearts of 72 rats were perfused with a buffer containing glucose (5.5 mM) and hexanoate (0.5 mM). They were maintained in normoxia for 30 min and then subjected to low-flow ischemia (0.5% of the preischemic coronary flow for 20 min) followed by reperfusion (45 min). From the beginning of ischemia, the perfusate was subjected to various changes: enrichment with GIK solution, enrichment with lactate (2 mM), enrichment with pyruvate (2 mM), enrichment with pyruvate (2 mM) plus ethanol (2 mM), or no change for the control group. Left ventricular developed pressure, heart rate, coronary flow, and oxygen consumption were monitored throughout. The lactate/pyruvate ratio of the coronary effluent, known to reflect the cytosolic NADH/NAD(+) ratio and the fructose-6-phosphate/dihydroxyacetone-phosphate (F6P/DHAP) ratio of the reperfused myocardium, were evaluated. Mitochondrial ROS production was also estimated. The GIK solution improved the recovery of mechanical function during reperfusion. This was associated with an enhanced cytosolic NADH/NAD(+) ratio and reduced mitochondrial ROS production. The cardioprotection was also observed when the hearts were perfused with fluids known to increase the cytosolic NADH/NAD(+) ratio (lactate, pyruvate plus ethanol) compared with the other fluids (control and pyruvate groups). The hearts with a high mechanical recovery also displayed a low F6P/DHAP ratio, suggesting that an accelerated glycolysis rate may be responsible for increased cytosolic NADH production. In conclusion, the cardioprotection induced by GIK solutions could occur through an increase in the cytosolic NADH/NAD(+) ratio, leading to a decrease in mitochondrial ROS production.