EARLY COLLATERAL AND MICROVASCULAR ADAPTATIONS TO INTESTINAL ARTERY-OCCLUSION IN RAT

The technique to repeat edly observe exactly the same vessels in the r at intestine was used to investigate vascular compensation during the Ist wk after abrupt arterial ligation. A collateral-dependent tissue r egion was created by ligation of three to four sequential intestinal a rteries. At the center of the collateral-dependent region, arterial pr essure decreased from 96 +/- 3.7 to 29 +/- 2.5 mmHg, and intestinal bl ood flow fell similar to 80% during maximal dilation initially postlig ation. One week later, pressure and blood flow at the center had incre ased 31 and 250%, respectively. Relative to preligation values, the on ly compensatory adaptation was an enlargement (31 +/- 11%) of the coll ateral arteries located between normal tissue and the center; no incre ase was observed in the diameter or numbers of arterioles or collatera l arteries at the center. Wall shear rate was increased 173 +/- 35% in itially postligation at the site where luminal enlargement occurred. T he selective enlargement of collateral arteries away from the center r egion is consistent with the hypothesis that collateral enlargement is induced by chronic increases in wall shear rate and can occur indepen dently of tissue ischemia.