Age-related superior mesenteric arterial flow changes in piglets: effects of feeding and hemorrhage

Cardiovascular (CV) responses to feeding before and after 15% blood volume hemorrhage (H) were studied in lightly anesthetized piglets less than or equal to 2-days and greater than 2-wk-old. Superior mesenteric (Mes) and renal (Ren) arterial flows (F) were registered by electromagnetic probes before and continuously for 2 h after milk feeding (26 ml/kg) by gavage. Postprandially, in piglets less than or equal to 2-days-old MesF tended to increase (maximum change, mean +/- SE, 16.0 +/- 4.7%) at 30 min, whereas Mes vascular resistance (R) significantly decreased at 30, 90, and 120 min (17.3 +/- 6.2%). In piglets greater than 2-wk-old, MesF significantly increased by 30 min, which lasted 120 min (37.7 +/- 11.7%); MesR decreased by 20.0 +/- 5.8% at 90-120 min. Compared with the less than or equal to 2 days olds, the older piglets demonstrated greater and more sustained postprandial MesF increase. After H, regional F and pulse pressure (PP) decreased, heart rate and R increased in both groups. After stabilization, feeding induced insignificant CV changes in less than or equal to 2-day-old piglets. In contrast, increased MesF (44 +/- 14.4%) and PP (24 +/- 8.5%) and decreased MesR (31 +/- 8.9%) were observed in the greater than 2-wk-olds. MesF changes differed significantly between the age groups. The Ren vascular bed showed no consistent response in both age groups. Thus Mes vascular responses to feeding with or without preceding H in developing piglets were age related.