Pressure modulates the reactivity of isolated rabbit epicardial arteries

1. The magnitude of responses to prostaglandin F2 alpha (PGF2 alpha) and adenosine (ADO) in pressurized rabbit epicardial coronary arteries (367 +/- 44 microns o.d.) with intact endothelium was assessed when they developed spontaneous tone. 2. The arteries were cannulated and changes in arterial diameter registered with an automated video perfusion system. The vessels, in the stabilization period at 60 mmHg, were divided into two groups, one exposed to a longitudinal stretch of +20% of unstretched initial length (Lo), and the other to +35% Lo, which developed spontaneous tone. In both cases, diameter-pressure curves were obtained by changing the intravascular pressure from 30 to 120 mmHg in aleatory steps of 30 mmHg (dp/dt = 15 mmHg s-1). 3. Diameter reduction of the arteries with stretch of +35% Lo in response to 1 microM PGF2 alpha was greater than that with stretch of +20% Lo. Likewise, increase of the arteries that had +35% Lo in response to 1 microM ADO was greater than with +20% Lo. 4. Intravascular flow (40 microliters min-1) increased the tone level of arteries. The addition of PGF2 alpha enhanced this tone which was similar to that obtained with a stretch of +35% Lo and no flow, whereas the effect of ADO was increased. 5. These data indicate that the vasomotor responses of PGF2 alpha and ADO are modulated by the degree of longitudinal stretch in epicardial arteries.