Tag: John Halliwill

Effects Of Histamine-Receptor Blockade And Exercise On Blood-Glucose Concentration

Presenter(s): Sabrina Raqueno-Angel − Human Physiology

Faculty Mentor(s): John Halliwill, Matt Ely

Poster 23

Research Area: Natural Science

Funding: OURS Program, the Oregon Undergraduate Researchers in SPUR (Summer Program for Undergraduate Research in Life Sciences)

Histamine is a molecular transducer released from mast cells during exercise, and its role during the exercise period is unknown. The experiment’s purpose was to determine if H1/H2 histamine receptor blockades would decrease blood-glucose concentrations during exercise. It was hypothesized that histamine receptor blockade would decrease blood-glucose concentrations during exercise. Subjects were chosen if ages 18-40, had a BMI of ≤ 25 kg/m2, experience riding/racing bikes, and can perform 3 hours of continuous exercise. The independent variable was the pill taken (antihistamine or placebo), and the dependent was blood-glucose concentration. After a screening and two familiarization visits, the subject completed four study visits, in which they performed a 120-minute cycling exercise at 50% VO2 max on a stationary bike in a temperature and humidity-controlled room. Before each study visit, the subject was randomly given a placebo pill or antihistamine and rested for two hours. Measurements were taken from the earlobe pre-exercise and three times during exercise at 15, 60, and 120 minutes. Repeated-measures two-way ANOVA (RM ANOVA, Group X Time) was used for statistical analysis. No differences were found between placebo and antihistamine groups (p = 0.801), and no Group X Time Interaction was determined (p = 0.881). Blood glucose levels at 15, 60, and 105 minutes were lower than the pre-exercise levels (p<0.001). No significant differences in blood-glucose concentrations were found between placebo and antihistamine groups. This research provides valuable information regarding histamine’s role in the cardiovascular system’s physiological pathways, which is important for forming cardiovascular disease prevention.

Exercise-induced Elevations in Skeletal Muscle Histamine Contributes to Increased Post- exercise Capillary Permeability

Exercise-induced Elevations in Skeletal Muscle Histamine Contributes to Increased Post- exercise Capillary Permeability

Chaucie Edwards

Faculty Mentor(s): John Halliwill & Matthew Ely

Oral Session 4 S

Histamine, an endogenously released molecule in immune and inflammatory responses increases local vasodilation, blood flow, and capillary permeability. During exercise, histamine is produced within exercising muscle and contributes to an elevated post-exercise blood flow. The histamine-induced post-exercise vasodilation is contained within previously exercised muscle as histamine concentrations are not elevated in non-exercised muscle (i.e. arms during leg exercise). It is unknown if intramuscular histamine also contributes to elevate capillary permeability following exercise. PURPOSE: To compare capillary permeability of the leg before and after prolonged unilateral knee-extension exercise under normal conditions and when histaminergic signaling is blocked. It was hypothesized that H1/H2 receptor antihistamines would decrease capillary permeability following exercise in an exercised leg but not in a resting leg. METHODS: Six (2F) volunteers performed 60 min of unilateral knee-extension exercise at 60% of peak power after consuming either Placebo or histamine (H1/H2) receptor antagonists (Blockade). A capillary filtration coefficient (CFC) reflecting the rate of change in limb girth per rise in venous pressure was calculated using venous occlusion plethysmography. A CFC was calculated prior to (PRE) and following (POST) exercise in both the exercised leg (EL) and the resting leg (RL). Data were analyzed with a 3-way RM ANOVA and presented as Means±SEM. RESULTS: On average, CFC increased 161±90% (PRE: 2.5±1.0 to POST: 6.6±2.3 μg·100g-1·min- 1·mmHg-1) in the EL and 38±31% (PRE: 4.8 to POST: 6.5 μg·100g-1·min-1·mmHg-1) in the RL during Placebo. Blockade attenuated the exercise-induced rise in CFC in the EL to 13±41% (PRE = 4.3±1.3 to POST = 4.9±1.8 μg·100g-1·min-1·mmHg-1) and in the RL 2±45% (PRE: 3.8±1.4 to POST: 3.8±1.7 μg·100g-1·min-1·mmHg-1). Due to the high variability in the measures there was a trend for CFC to increase with exercise (P=0.161), for Blockade to attenuate the rise in CFC (P=0.363), and for a leg by drug interaction (P=0.289). CONCLUSION: These initial data suggest that exercise-induced histamine production contributes to the elevated CFC within exercised limbs.