Lactoferrin is a milk protein that reportedly protects infants from gut-related, systemic infection. Proof for this concept is limited and was addressed during in vivo and in vitro studies. Neonatal rats pretreated orally with recombinant human lactoferrin (rh-LF) had less bacteremia and lower disease severity scores (P < 0.001) after intestinal infection with Escherichia coli. Control animals had 1,000-fold more colony-forming units of E. coli per milliliter of blood than treated animals (P < 0.001). Liver cultures from control animals had a twofold increase in bacterial counts compared with cultures from rh-LF-treated pups (P < 0.02). Oral therapy with rh-LF + FeSO(4) did not alter the protective effect. In vitro studies confirmed that rh-LF interacted with the infecting bacterium and rat macrophages. An in vitro assay showed that rh-LF did not kill E. coli, but a combination of rh-LF + lysozyme was microbicidal. In vitro studies showed that rat macrophages released escalating amounts of nitric oxide and tumor necrosis factor-alpha when stimulated with increasing concentrations of rh-LF. The in vitro studies suggest that rh-LF may act with other "natural peptide antibiotics" or may prime macrophages to kill E. coli in vivo.

Prophylactic therapy with recombinant human lactoferrin and the probiotic, Lactobacillus GG, act to enhance defenses against invasive E. coli in the nascent small intestine. We suggest that rhLF and LGG are therapeutic agents that may reduce necrotizing enterocolitis and gut-related sepsis in preterm human infants.

Antimicrobial proteins and peptides are key effectors of innate immunity at mucosal surfaces in adult animals (21), but their role in host defense during perinatal intestinal development is not clearly delineated. Paneth cells are specialized epithelia in the crypts of the small bowel that control the intestinal growth of bacterial pathogens through the secretion of antimicrobial proteins and peptides (11). Paneth cells secrete their antimicrobial-rich granules upon exposure to pathogenic bacteria and bacterial products (1,11,12), and alphadefensins account for 70% of the secreted bactericidal activity of Paneth cells (1).Neonatal necrotizing enterocolitis is a disease mainly of preterm human infants, but its pathogenesis is incompletely understood (8). It is hypothesized that abnormal bacterial colonization of the small bowel plays a role (3). A causative association between Paneth cells and necrotizing enterocolitis has been proposed because preterm infants inadequately express alpha-defensins in the small bowel (10). Additionally, Paneth cells in surgical specimens from human infants with necrotizing enterocolitis have a deficiency in lysozyme (4), a prominent antimicrobial protein in Paneth cell granules (11). The inability of neonatal Paneth cells to control the growth of bacterial pathogens in the lumen of the small bowel is an attractive hypothesis related to the initiation of necrotizing enterocolitis, but there is no in vivo evidence that Paneth cells provide host defense in the neonatal small bowel.This investigation postulated that ablating Paneth cells in neonatal rats would reduce the ability of the neonatal small bowel to clear an infection caused by enteroinvasive Escherichia coli. To test this hypothesis, dithizone was given systemically to neonatal rats. Since dithizone selectively destroys Paneth cells in adult rats (16), we quantified the effects of dithizone on the Paneth cells of neonatal rats. After dithizone treatment, newborn rats were infected with an intragastric dose of Escherichia coli, and the quantitative clearance of this bacterium from the small bowel lumen was measured.Effect of dithizone on Paneth cells in the noninfected neonatal small bowel. For studies that examined the effects of dithizone, specific-pathogen-free Sprague Dawley rats (Harlan, San Diego, CA) were studied between 4 and 5 days of age. The studies described below were approved by the Animal Use Committee of the University of California, Davis.Dithizone (Sigma-Aldrich, St. Louis, MO) was suspended in 25 mM Li 2 CO 3 buffer, stirred for 2 h at 37°C, and then filtered through preweighed Whatman 1 paper (Whatman Inc., Clifton, NJ). The filter paper was completely dried after filtration and was reweighed to determine the mg/ml of dissolved dithizone. The measurement of dissolved dithizone was used to properly dose administration of the dye.Three separate litters of 4-day-old pups were given an intraperitoneal (i.p.) injection of either filter-sterilized dithizone (75 mg/kg of body weight) in mM Li 2 CO 3 buffer, 25 mM...

This study examined the effect of dynamic exercise on vasopressin release in the miniswine and factors that may elicit this response (n = 15). Thus lysine vasopressin (LVP), the catecholamines epinephrine and norepinephrine (EPI and NE), plasma renin activity (PRA), and plasma volume, Na+, and osmolality were measured before and during treadmill running at work intensities of 60, 80, and 100% of each swine's maximal heart rate reserve (HRR). LVP increased in a progressive manner similar to that of humans, ranging from 5.9 +/- 0.4 pg/ml before exercise to 30.1 +/- 4.5 pg/ml during maximal exercise. EPI, NE, and PRA [an index of angiotensin II (ANG II) activity] demonstrated a pattern of response comparable to LVP. Although these hormones can influence the release of LVP, only PRA displayed a strong correlation with LVP (r = 0.84). When ANG II synthesis was blocked (captopril, 1-3 mg/kg, intra-atrial injection) during exercise (80% HRR), plasma LVP was reduced from 9.9 +/- 0.6 to 7.5 +/- 0.6 pg/ml (P < 0.05). In addition, moderate-to-strong correlations were found between plasma concentrations of LVP and plasma osmolality (r = 0.79) and body temperature (r = 0.78). Plasma LVP also correlated with decreases in plasma volume (r = 0.84). These data suggest that the miniswine model is a good one for studying vasopressin effects during exercise and that ANG II appears to be a particularly strong stimulus for the release of this hormone.

No abstract