Ranadive, Sushant

Exercise‐induced rapid onset vasodilation produces a temporary rise in skeletal muscle blood flow in humans. The underlying mechanisms for this rapid hyperemia and regulation of muscle blood flow with single contraction are still not well understood. We tested the hypothesis that during a prolonged high dose intrarterial infusion of adenosine triphosphate (ATP; 20 μgrams ·100 mL forearm vol −1 ·min −1 ), the rapid onset vasodilatory response post‐single exercise contraction would be reduced compared to that of adenosine (ADO; 23 μgrams ·100 mL forearm vol −1 ·min −1 ). 14 healthy young participants (30 ± 1 years) performed a forearm single contraction exercise (20% of maximum) at minute 75 of either ATP (N=8) or ADO (N=6) continuous infusion. Artery diameter and blood velocity were measured using Doppler ultrasound. Forearm vascular conductance (FVC; ml·min −1 ·100 mmHg −1 ), time to peak, and area under curve were calculated. The mean resting FVC was higher during ATP (307.15 ± 50.56) and ADO (353.23 ± 43.98) infusion compared to saline infusion (45.17 ± 5.61 and 47.14 ± 5.57) (p<0.05). Compared to ADO, ATP infusion had a lower delta FVC from post‐ to pre‐contraction (174.06 ± 30.75 vs. 276.53 ± 24.90, p<0.05). Area under the curve and time of peak FVC did not significantly differ between drugs. These results suggest a prolonged ATP infusion may have blunted the rapid vasodilatory response more‐so than ADO. Thus, our findings indicate that ATP may be necessary but not obligatory in the rapid onset vasodilation response post‐single muscle contraction in humans. Support or Funding Information Supported by National Institutes of Health Research Grants HL‐119337 (to M.J. Joyner and F.A. Dinenno) and by CTSA UL1 TR000135. The Caywood Professorship (M.J. Joyner) via the Mayo Foundation also supported this research.

<a name=“OLE_LINK2”></a><a name=“OLE_LINK1”>Hypertensive pregnancy (HP) disorders have been linked to a four‐fold increased risk for development of future cardiovascular diseases. We examined whether history of HP in postmenopausal women (N=20, 59±5 yr) influenced the risk factors for cardiovascular disease as assessed by aortic pulse wave characteristics, compared to age and parity matched controls (N=18, 60±4 yr). Non‐invasive aortic pressure waveforms were synthesized from high‐fidelity pressure waveforms obtained from SphygmoCor applanation tonometry using the radial artery. Aortic systolic and diastolic blood pressure (ASBP, ADBP), aortic augmentation index (AI x ), augmented pressure (AP), aortic pulse pressure (APP), and left ventricular wasted energy (E w ) were calculated from the generated aortic pressure waveform. There were no differences in ASBP (125±4 vs. 129±4 mmHg), ADBP (79±2 vs. 81±2 mmHg), AP (17±2 vs. 17±2 mmHg), AI x (35±2 vs. 29±1%), AI x @75BPM (31±2 vs. 29±1%), E w (3313±338 vs. 3364±432 dynes/cm 2 /s), between women with a history of HP vs. matched controls, respectively (P>0.05 for all). Body mass index was significantly higher in women with a history of HP (30.6±1 vs. 26.7±1 kg/m 2 , P<0.05), however it did not statistically influence any of the indices (P>0.05 for all). Our results suggest that postmenopausal women with a history of HP do not demonstrate elevated aortic blood pressure or altered aortic pulse wave characteristics in comparison to matched controls. </a> Supported by: National Institute of Aging 1P50AG044170‐01 and CTSA UL1 TR000135 and HL 118154

Hyperoxia can cause substantial reductions in peripheral and coronary blood flow at rest and during exercise. We tested the hypothesis that hyperoxia may increase the time for forearm blood flow (FBF) to reach steady state (SS) levels during exercise. Young (n=11; 28±2yr) healthy adults performed rhythmic forearm contractions at 10% of their maximum voluntary contraction for 5 minutes. Each duty cycle consisted of 1 second contraction and 2 second relaxation. Brachial artery diameters and velocities were measured using Doppler Ultrasound and forearm blood flow (ml/min) was calculated from the mean velocity and diameter. The dynamics of FBF at the onset of exercise were assessed by calculating the slope of the FBF response for every duty cycle between baseline and steady state, and the number of duty cycles to reach steady state. The slope of the line plotted from baseline FBF to SS, had a significantly attenuated slope under hyperoxia (5.4±1.1 ml/min/cycle) as compared to normoxia (10.6±2.6 ml/min/cycle). In addition, the number of duty cycles performed under hyperoxia (33±4 cycles) was significantly higher as compared to normoxia (25±4 cycles) (P<0.02). Our data suggest that hyperoxia attenuates the contraction‐induced FBF from baseline to SS as compared to normoxia.