COMPARISON OF CONDUIT VESSEL AND RESISTANCE VESSEL REACTIVITY - INFLUENCE OF INTIMAL PERMEABILITY

Arterioles of hamster cheek pouches are less reactive to luminal appli cation of small hydrophilic agents than to adventitial application. To explore possible longitudinal variations in response sidedness, we co mpared reactivity of isolated vessels from carotid arteries to first-o rder arterioles. Concentration-response curves for luminally or advent itially applied phenylephrine (PE) were constructed. Arterioles were 2 74-fold less responsive when PE was applied luminally than when applie d adventitially. Differences in luminal vs. adventitial responsiveness decreased as vessel diameters increased, from 24-fold in inferior sac cular arteries to 18-fold in external maxillary arteries and, finally, to 3-fold in common carotid arteries. Differences in response to lumi nal or adventitial application of PE could be eliminated in arterioles by perfusion with olamidopropyl)-dimethylammonio]-1-propanesulfonate (CHAPS), which disrupts membrane integrity. Treatment with CHAPS also increased the transmural movement of sodium fluorescein across arterio lar vessel walls. We conclude that a diffusion barrier exists in arter ial walls, that there is a longitudinal variation in this barrier as e xpressed by the differences in movement of small hydrophilic molecules from lumen to smooth muscle cell layers, and that the site of the bar rier is likely to be at the endothelial cell membrane.