Determination of an optimal axial-length tension for the study of isolatedresistance arteries on a pressure myograph

The effects of longitudinal stretch on vasoreactivity were assessed in isol ated, pressurised arteries from the rat mesentery, rat mid-cerebral and hum an subcutaneous vascular beds. A stretch-dependent increase in reactivity w as observed only in rat third order mesenteric arteries. Longitudinal stret ch greater than or equal to 20 % (force equal to 0.23 +/- 0.04 mN) optimise s vasoconstrictor responses to noradrenaline and phenylephrine in rat third order mesenteric arteries. Stretch did not affect the vasoconstriction res ponse to depolarisation by 30 mM K+ PSS in any of the arteries studied. Sim ilarly, stretch had no affect on pressure-dependent myogenic responses in r at mid-cerebral arteries. Endothelium-independent and endothelium-dependent mechanisms of vasorelaxation were unaffected by stretch in rat third order mesenteric arteries. Likewise, stretch did not affect vasoreactivity in ra t mid-cerebral and human subcutaneous resistance arteries. Our results show that longitudinal stretch in isobaric-mounted rat third order mesenteric a rteries is an important methodological consideration. Considering our resul ts, we recommend that isobaric-mounted rat third order mesenteric arteries are stretched greater than or equal to 20 % to provide optimal experimental conditions for pharmacological studies.