The influence of preload on the reactivity of coronary arteries

: Usually, blood vessel preparations used for in vitro investigations are kept under a certain passive preload. This preload influences the blood vessel reactivity against agonists. Using transverse strips of porcine coronary arteries (Ramus circumflexus) the influence of preload on the amplitude of blood vessel responses induced by acetylcholine, potassium ions and prostaglandin F2 alpha was tested. The optimum preload to obtain a maximum contraction was 1.92 +/- 0.14 g. This value did neither depend on the agonist nor its concentration. However, there was a direct relation between the size of the vessel preparation and the value of the optimum preload. Thus, it is worth taking into account the correct preload when blood vessel preparations are tested in vitro.