The cardiovascular and respiratory effects of intravenous adenosine were studied in conscious normal volunteers. Bolus injections of adenosine increased systolic and diastolic pressures initially (+ IS and +13 mm Hg after 100 jug/kg) followed by a subsequent reduction in systolic and diastolic pressures (-12 and -16 mm Hg). Heart rate increased during trough blood pressure (R-R interval shortening of 298 msec after 100 /xg/kg). Adenosine steady-state infusions increased heart rate ( + 30 beats/min during 140 /xg/kg/min), systolic pressure ( + 16 mm Hg), and pulse pressure ( + 21 mm Hg) but decreased diastolic pressure slightly (-5 mm Hg), resulting in no significant change in mean arterial pressure. Adenosine stimulated respiration, resulting in decreased Paco 2 (41 to 31 mm Hg), increased Pao 2 (101 to 113 mm Hg), and increased pH (7.42 to 7.50). The increased ventilation was not explained by bronchoconstriction, hypotension, or hypoxia. The observed pressor and tachycardic effects are mediated through reflex autonomic mechanisms since they are completely abolished in patients with severe autonomic failure. These autonomic mechanisms probably involve chemoreceptor activation since adenosine is pressor when infused in the aortic arch proximal to the origin of the carotid arteries but depressor when infused in the descending aorta. It is concluded that the hemodynamic and respiratory effects of adenosine observed in normal volunteers are in part due to chemoreceptor stimulation. These findings raise the possibility that adenosine is an endogenous, modulator of respiration in man.

We hypothesized that the endogenous coronary vasodilator adenosine may reduce infarct size by progressively increasing reflow in a preparation of coronary occlusion-reperfusion. After 90 min of proximal left anterior descending artery occlusion, 20 dogs were randomized to blood reperfusion with (n = 10) or without (n = 10) adenosine into the proximal left anterior descending vessel at 3.75 mg/min for 60 min after reperfusion. Regional myocardial blood flow was determined serially with microspheres and regional ventricular function was assessed by a computerized radial shortening method. At 24 hr, the area at risk was defined in vivo with monastral blue dye and area of necrosis was determined after incubation of left ventricular slices in triphenyltetrazolium chloride. Hemodynamic variables were similar in the two groups during the experimental protocol. Infarct size was significantly reduced in treated animals, both when expressed as a percentage of the area at risk (9.9 2.8% vs 40.9 + 6.6%, p < .001) and as a percentage of the left ventricle (4.6 ± 1.3% vs 18.0 ± 3.4%, p = .002). This was associated with significant improvement in radial shortening in the ischemic zone 24 hr after reperfusion (10. 1 ± 2.5 vs -2.8 + 2.2%, p < .01). Regional myocardial blood flow was significantly increased in endocardial and epicardial regions from the lateral ischemic zone 1 hr after reperfusion in adenosine-treated animals. Light microscopy demonstrated decreased neutrophil infiltration in the ischemic zone and electron microscopy showed relative preservation of endothelial structure in the subendocardium with reduced neutrophil and red cell stagnation ofcapillaries in the treated group. These findings suggest that intracoronary administration of adenosine after reperfusion significantly reduces infarct size and improves regional ventricular function in the ischemic zone in the canine preparation.

Because micronutrients from plants may have beneficial cardiovascular effects, the hypothesis that an encapsulated juice powder concentrate might affect several measures of vascular health was tested in free living adults at low cardiovascular risk. Blood pressure, vascular compliance, lipid and antioxidant markers, and serial electron beam tomography (to calculate a coronary artery calcium score as a measure of atherosclerosis burden), were monitored in 51 pre-hypertensive and hypertensive subjects over 2 years. By the end of follow-up, systolic and diastolic blood pressure decreased significantly (−2.4 ± 1.0 mmHg, P < 0.05 and −2.2 ± 0.6 mmHg, P < 0.001), and large artery compliance improved significantly (1.9 ± 0.6 ml mmHg−1 × 100, P < 0.01). The progression of coronary artery calcium score was smaller than expected compared with a historical database (P < 0.001). Laboratory testing showed a significant decrease in homocysteine (P = 0.05), HDL cholesterol (P = 0.025) and Apo A (P = 0.004), as well as a significant increase in β-carotene, folate, Co-Q10 and α-tocopherol (all P < 0.001). The phytonutrient concentrate we utilized induced several favorable modifications of markers of vascular health in the subjects. This study supports the notion that plant nutrients are important components of a heart healthy diet.

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