Effect of Increased Skeletal Muscle Temperature on Intramuscular Histamine Concentrations
Authors: Mangum Joshua , Sieck Dylan , Ely Matthew , Larson Emily , Minson Christopher , Halliwill John 
Published: June 2021

Intramuscular concentrations of histamine are increased by ~40% following 60 minutes of aerobic exercise. This rise in intramuscular histamine is due to both mast cell degranulation and formation of histamine by histidine decarboxylase. This results in histamine receptor activation, which plays a critical role in mediating the sustained blood flow response following a bout of aerobic exercise. A previous study determined that oxidative stress is not the cause for the sustained blood flow response following exercise; however, other exercise factors such as increased temperature, decreased pH, movement/vibration of muscle, and other stimuli have not been investigated as potential signals for histamine release. Some in vitro evidence suggests that changes in temperature can cause both the degranulation of mast cells as well as increase the activity of histamine decarboxylase. Therefore, the purpose of this study was to determine if an in vivo increase in skeletal muscle temperature. Mimicking the magnitude and time‐course that is observed during dynamic, one‐legged knee‐extension exercise, is sufficient stimulus to provoke intramuscular histamine release in skeletal muscle. Specifically, we hypothesized that heating skeletal muscle up to 39°C (a temperature which we previously noted during 60 min of dynamic, one‐legged knee‐extension exercise) would result in increases in intramuscular histamine concentrations that are closely matched to exercising values. Seven moderately active, healthy volunteers (2F) participated in this study. Sixty min of short‐wave diathermy (Megapulse II, Accelerated Care Plus) was used to raise skeletal muscle (vastus lateralis) temperature to ~39°C. Previous testing had identified the target of 39°C, the temperature of skeletal muscle during dynamic, one‐legged kicking aerobic exercise. Skeletal muscle temperature was measured via an intramuscular thermocouple and skeletal muscle microdialysis was used to measure intramuscular dialysate histamine concentrations. During the 60 min heating session, intramuscular temperature was recorded every 10 min and skeletal muscle dialysate was collected prior to heating and every 20 min during heating. Heart rate and blood pressure were monitored and recorded throughout the study. Prior to heating, skeletal muscle temperature was 32.4°C ± 0.4 and was increased to 38.1°C ± 0.7 by the end of heating (p<0.05). The time course of change in temperature during heating was similar to what was previously observed with aerobic exercise. Sixty minutes of heating increased intramuscular histamine concentrations from 2.12 ± 0.17 ng/ml to 2.90 ± 0.20 ng/ml (p<0.05), an increase of ~37%. There were no significant changes in heart rate nor blood pressure in response to heating. In conclusion, mimicking the magnitude and time‐course of increasing skeletal muscle temperature observed during aerobic exercise results in an increase in intramuscular histamine that closely match the exercise histamine response values. These data suggest that the increase of skeletal muscle temperature during exercise plays an important role in the release or synthesis of histamine within skeletal muscle.Support or Funding InformationSupport provided by NIH grant HL115027This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.