Unexpected changes in the catecholamine content of platelets and plasma during exercise

Area of Science:

• Exercise Physiology
• Biochemistry
• Hematology

Background:

• Platelets retain catecholamines for extended periods post-plasma normalization.
• Platelet catecholamine levels may serve as indicators of transient plasma elevations.

Purpose of the Study:

• To investigate if platelet catecholamine concentrations can index short-term plasma adrenaline (A) and noradrenaline (NA) surges.
• To examine the response of plasma and platelet catecholamines during maximal and submaximal exercise protocols.

Main Methods:

• Seven healthy males (22-34 years) underwent supramaximal (Max) and submaximal (Submax) cycling protocols.
• Plasma and platelet catecholamine concentrations, along with circulating platelet counts, were measured.

Main Results:

• Plasma A and NA significantly increased during Max and Submax exercise.
• Platelet A and NA concentrations decreased during the initial 15 minutes of exercise in both protocols.
• Circulating platelet counts nearly doubled during exercise, returning to baseline during recovery.

Conclusions:

• Exercise initiates a rapid increase in plasma catecholamines and platelet count, accompanied by a decrease in platelet catecholamine levels.
• This suggests the release of catecholamine-free platelets, likely from the spleen, at exercise onset.
• The underlying reasons for sequestered, catecholamine-free platelets in the spleen require further investigation.