Age-Dependent Changes in the Postnatal Intestinal Microcirculation

Abstract

Significant changes occur in intestinal hemodynamics during the transition from fetal to newborn life and then again during the first postnatal month. Most importantly, basal vascular resistance substantially decreases following birth. It then decreases further between postnatal days 1 and 3, plateaus, and then begins a slow, progressive increase between postnatal days 12 and 30. The basal rate of intestinal blood flow mirrors the changes in vascular resistance in an inverse manner. The postnatal changes in vascular resistance appear to be mediated, in large part, by an increase in the constitutive and stimulated production of nitric oxide. Most importantly, the diameter of terminal mesenteric arteries (150-300 m diameter) in newborn (i.e., 1 day old) swine is determined by three intrinsic vascular control systems: endothelial production of nitric oxide and endothelin, and the inherent myogenic response of vascular smooth muscle. In contrast, these vessels in older subjects (i.e., 35 days old) are primarily passive in nature and fail to demonstrate significant diameter change in response to blockade of endogenous nitric oxide production or endothelin receptors, or applied perturbations of pressure or flow rate. The circulatory physiology of the perinatal and newborn intestine is exceptional when compared to the adult condition inasmuch as several hemodynamic variables change quite dramatically between fetal and neonatal life and during the first postnatal month. The unique hemodynamic conditions that characterize the perinatal and newborn intestine appear to be part of the overall physiological transition that occurs as the fetus, once born, replaces the placenta with his gastrointestinal tract to obtain nutrition. The goal of this review is to describe the circulatory physiology of the perinatal and newborn intestine, with a particular emphasis on those portions of the intestinal microcirculation that have thus far been studied. First, however, it is important to discuss the age-dependent changes that occur within the intestinal circulation during perinatal and early newborn life. Microcirculation (2001) 8, 377-387.

Factors that influence mesenteric artery blood flow velocity in newborn preterm infants

“…The role of constitutive NO production in setting basal intestinal vascular resistance is also greater in newborn piglets. 1,24 It is unclear, however, whether these factors relate to our findings of lower SMA BFV in parenterally fed infants. Studies are also needed to determine if HAL has effects on SMA BFV and intestinal maturation that are independent of enteral feeding volumes.…”

Gastrointestinal Function Regulation by Nitrergic Efferent Nerves

“…Basal vascular resistance decreased following birth, then decreased further, and began to increase between postnatal days 12 and 30 (Nankervis et al, 2001). These changes appear to be largely mediated by an increase in the production of NO from the endothelium and possibly from the perivascular nerves.…”

The stress of maternal separation causes misprogramming in the postnatal maturation of rat resistance arteries

“…Vascular resistance and BP increase throughout postnatal maturation, along with dynamic changes in the regulation of blood flow in the regional circulations (7,36,48). It has been suggested, based mostly on epidemiological studies, that stressors in critical periods of developmental maturation may permanently reprogram arterial function and BP (reviewed in Ref.…”