Effect of increased tissue oxygen uptake on autoregulation in postnatal intestine.

To determine whether the rate of tissue oxygen utilization affects pressure-flow autoregulation in an age-dependent fashion in postnatal swine intestine, in vitro gut loops from 3- and 35-day-old swine were subjected to a 35% step reduction in arterial pressure under control conditions, during intra-arterial infusion of 2,4-dinitrophenol (DNP), and 30 min after luminal instillation of predigested artificial swine milk. Autoregulation was quantitated by determining the effect of pressure reduction on vascular resistance, and also by calculating Gf, a flow-controlling gain factor that relates pressure and flow. DNP infusion increased oxygen uptake 77 and 58% in gut from 3- and 35-day-old swine, respectively, whereas feeding increased oxygen uptake approximately 50% in both groups. Under control conditions, arterial pressure reduction had no effect on vascular resistance in either group. During DNP infusion and 30 min after feeding, however, intestine from 35- but not from 3-day-old swine demonstrated significant vasodilation in response to pressure reduction. Gf averaged -0.06 +/- 0.11 vs. 0.21 +/- 0.08 (P < 0.05) before vs. DNP infusion, and 0.06 +/- 0.03 vs. 0.22 +/- 0.06 (P < 0.05) before vs. 30 min after feeding in intestine from 35-day-old swine; these increases in Gf indicate that the intensity of the pressure-flow response increased during experimental treatments. In contrast, Gf averaged -0.11 +/- 0.07 vs. -0.23 +/- 0.08 before vs. DNP infusion, and -0.23 +/- 0.06 vs. -0.23 +/- 0.09 before vs. 30 min after feeding in intestine from 3-day-old swine.(ABSTRACT TRUNCATED AT 250 WORDS)