Regulation of capillary exchange capacity in postnatal swine intestine

To determine whether intrinsic regulation of capillary exchange capacity is age-dependent during early postnatal life, we measured the capillary filtration coefficient (Kf,c), an index of capillary exchange capacity, within isolated perfused intestine from 3- and 35-day-old swine at different arterial pressures. Kf,c was determined gravimetrically, by means of the flow-equilibration technique. During baseline perfusion at age-appropriate pressures, Kf,c averaged 0.203 +/- 0.020 vs. 0.361 +/- 0.040 ml.min-1 x mmHg-1 x 100 g in 35- vs. 3-day-old intestine. In older animals, a progressive rise in Kf,c was noted as arterial pressure was lowered: Kf,c increased 14, 35, and 98% above baseline when pressure was reduced 20, 40, and 60% below baseline, respectively. An inverse linear correlation between Kf,c and blood flow was demonstrated in this group. Kf,c also increased in 3-day-old intestine during progressive hypotension, but these changes were of less magnitude: Kf,c averaged 19, 17, and 23% above baseline ...