Hyperthermia Augments the H1-Histamine Receptor-Mediated Force in the Human Atrium

Area of Science:

• Cardiology
• Pharmacology
• Physiology

Background:

• The effect of hyperthermia on histamine-mediated cardiac contractility via human H1-histamine receptors is not well understood.
• Histamine plays a role in cardiovascular function, but its interaction with temperature changes in the heart requires further investigation.

Purpose of the Study:

• To investigate whether hyperthermia enhances the efficacy of histamine in increasing cardiac contraction force through human H1-histamine receptors.
• To compare the effects of hyperthermia on histamine's cardiac action in human atrial preparations and in a mouse model.

Main Methods:

• Isolated human atrial preparations (HAPs) from patients with coronary heart disease were used.
• Transgenic mice overexpressing cardiac human H1-histamine receptors (H1-TG) were utilized for comparison.
• Cardiac contraction force was measured under varying temperature conditions (hyperthermia vs. hypothermia) with histamine stimulation.

Main Results:

• In H1-TG mice, histamine was less effective in increasing cardiac force under hyperthermia compared to hypothermia.
• Conversely, in human atrial preparations, histamine was more effective in augmenting force during hyperthermia than hypothermia.
• The contractile response to H1-histamine receptor activation showed opposite temperature dependencies in H1-TG mice and HAPs.

Conclusions:

• The temperature-dependent effects of histamine on cardiac contractility differ between H1-TG mice and human atrial preparations.
• In patients experiencing fever (hyperthermia), histamine may serve a compensatory role in preserving cardiac contractile function.