Direct visualization of the coronary microcirculation for pharmacologic and physiologic studies

Area of Science:

• Cardiovascular Physiology
• Microcirculation Research
• Pharmacology

Background:

• Assessing coronary microcirculation requires models that maintain physiological tone.
• Existing models often suffer from ischemic damage or lack direct visualization capabilities.
• A need exists for a robust preparation to study coronary vasodilation and reactivity.

Purpose of the Study:

• To describe a new isolated, arrested rat heart preparation.
• To enable direct visualization of the coronary microcirculation.
• To evaluate the preparation's utility in physiological and pharmacological studies.

Main Methods:

• Isolated rat hearts perfused in situ prior to isolation to prevent ischemic damage.
• Perfusate: modified Krebs solution with albumin and washed red cells.
• Fluorescence microscopy used with fluorescent albumin conjugate for direct microvessel visualization.

Main Results:

• The model exhibited an intercapillary distance of 33 microns, suggesting 60-70% capillary reserve.
• Nisoldipine induced dose-dependent coronary vasodilation with significantly enhanced reactivity compared to other models.
• Histamine caused vasodilation but not increased macromolecular permeability.

Conclusions:

• The described isolated, arrested rat heart preparation accurately reflects in vivo coronary tone.
• This model is well-suited for direct assessment of interventions on coronary tone and microcirculation.
• The preparation offers superior coronary reactivity for pharmacological studies.