Effects of distention and short-term grafting on vasoreactivity in rabbit external jugular veins.

The relative effects of distention, intraluminal pressure, and wall tension on venous smooth muscle and endothelial cell function were examined in 40 external jugular veins from New Zealand white rabbits. Vein grafts (n = 5) were interposed in the common carotid artery and explanted after 10 minutes. Distended veins were inflated in vitro with modified Krebs' solution at 37 degrees C for 10 minutes at pressures of either 20 mm Hg (D-20; n = 5) or 80 mm Hg (D-80; n = 5). Externally supported veins (ES-80; n = 5) were inflated at 80 mm Hg pressure, but distention was prevented by covering with a 3 mm internal diameter polytetrafluoroethylene sleeve. Bradykinin-induced in vitro maximal tension was attenuated significantly in vein grafts (0.13 +/- 0.04 g) and D-80 rings (0.27 +/- 0.07 g) compared with D-20 rings (1.20 +/- 0.14 g), ES-80 rings (0.99 +/- 0.13 g), or nondistended control rings (n = 40; 1.19 +/- 0.10 g; p less than 0.001). The attenuation in contraction in the vein graft and D-80 groups was nonspecific (i.e., similar results were obtained with respect to other smooth muscle agonists). Contractile function was inversely associated with wall tension, the product of pressure and radius (r2 = 0.7438; p = 0.06). In contrast, there were no differences in endothelium-dependent or endothelium-independent relaxation among the five groups. It is concluded that, in this experimental system, (1) venous smooth muscle function is significantly attenuated after short-term in vitro distention or grafting although endothelial function is largely preserved, and (2) the decrement in contraction is due to elevated wall tension.