In vitro time- and dose-effect response of JP-8 and S-8 jet fuel on alveolar type II epithelial cells of rats.

This study was designed to characterize and compare the effects of jet propellant-8 (JP-8) fuel and synthetic-8 (S-8) on cell viability and nitric oxide synthesis in cultured alveolar type II epithelial cells of rats. Exposure times varied from 0.25, 0.5, 1, and 6 hours at the following concentrations of jet fuel: 0.0, 0.1, 0.4, and 2.0 microg/mL. Data indicate that JP-8 presents a gradual decline in cell viability and steady elevation in nitric oxide release as exposure concentrations increase. At a 2.0 microg/mL concentration of JP-8, nearly all of the cells are not viable. Moreover, S-8 exposure to rat type II lung cells demonstrated an abrupt fall in percentage cell viability and increases in nitric oxide measurement, particularly after the 2.0 microg/mL was reached at 1 and 6 hours. At 0.0, 0.2, and 0.4 microg/mL concentrations of S-8, percentage viability was sustained at steady concentrations. The results suggest different epithelial toxicity and mechanistic effects of S-8 and JP-8, providing further insight concerning the impairment imposed at specific levels of lung function and pathology induced by the different fuels.

Insulin-like growth factor-I stimulates erythropoiesis when administered enterally.

BACKGROUND: Insulin-like growth factors I and II (IGF-I and IGF-II) are potent growth factors involved in development. IGF-I stimulates proliferation of erythropoietic progenitors and parenteral IGF-I administration stimulates in vivo erythropoiesis in animals. IGF-I and IGF-II are both present in mammalian milks and when milk-borne, are resistant to neonatal gastrointestinal degradation. Whether milk-borne IGF-I or IGF-II regulates neonatal erythropoiesis in not known. We hypothesized that physiological doses of enteral IGFs stimulate erythropoiesis in suckling rats. METHODS: Eight day-old Sprague Dawley rats were artificially fed for 4 days with rat milk substitute (RMS) or RMS supplemented with physiological levels of IGF-I or IGF-II. Rats fed IGF-I and IGF-II were compared to control RMS. Blood and marrow were collected; measures of red cell mass, measures of erythropoietic stimulus, and indices of iron status were measured. RESULTS: Rats fed IGF-I had higher hemoglobin (Hb) levels (100 +/- 10 g/l), compared to those fed RMS (94 +/- 9) or IGF-II (91 +/- 6), p < 0.001. After IGF-I supplementation, red blood cell counts (RBC) (p < 0.04) and hematocrits (p < 0.002) were also higher. Plasma erythropoietin (Epo) levels, reticulocytes, plasma iron and erythrocyte iron incorporation were similar. CONCLUSION: Intact enteral IGF-I reaches distal erythropoietic tissue resulting in greater red cell mass, but not by increasing plasma Epo levels or by altering cellular iron transport.

Iron-deficient erythropoiesis in neonatal rats.

Anemia in premature infants is extremely common. Precise quantitation of iron status and determination of iron incorporation into erythrocytes are important in monitoring therapy for anemia in premature infants, especially when treating with recombinant human erythropoietin (rhEPO). However, the traditional indices of the iron status have limited usefulness in this population. The goal of the current work is to develop an experimental animal model system that addresses the clinical issue relating to quantitation of iron delivery to erythrocytes. We first determined normal hematological values for nontreated, dam-suckled Sprague-Dawley rats by measuring markers of erythropoiesis and iron status during the first 12 postnatal days (PND). The experimental group of rats were administered parenteral rhEpo (430 IU.kg(-1). day(-1)) for 8 days (from PND 4 until PND 12) in the absence (rhEpo(-Fe)) or presence (rhEpo(+Fe)) of oral iron supplementation (6 mg.kg(-1).day(-1)). Rat pups receiving oral iron only (control(+Fe)) and pups that were sham fed with the orogastric tube (control(-Fe)) were included as controls. Hematological parameters were measured in blood and bone marrow. In a pattern similar to that seen in premature infants during the first 2 months of life, the levels of these hematopoietic markers were dynamic and changed during the first 12 PND. After challenging experimental animals with subcutaneous rhEpo, evidence of iron-deficient erythropoiesis was seen in the rhEpo(-Fe) group. Red blood cell levels and absolute reticulocyte counts were higher in both groups receiving rhEpo as compared with the controls. However, the rhEpo(-Fe) group experienced a lower hemoglobin level, a lower mean red cell volume, a greater red cell distribution width, and a higher zinc protoporphyrin/heme (ratio than the rhEpo(+Fe) group. The neonatal rat is an excellent model of iron-deficient erythropoiesis and will be useful in designing future mechanistic studies examining the interplay between iron and erythropoiesis in the anemic, iron-challenged premature neonate.

Erythropoietin stimulates vasculogenesis in neonatal rat mesenteric microvascular endothelial cells.

Human breast milk is a rich source of growth factors, including erythropoietin (Epo), the endogenous hormonal stimulant of erythropoiesis. Recombinant human Epo (rhEpo) has been shown to stimulate 1) angiogenesis, the process of new blood vessel growth from preexisting vessels; 2) vasculogenesis, tubule formation from single-cell suspensions; and 3) endothelial cell proliferation in immortalized endothelial cells and vessel explants. We hypothesized that Epo would induce mitogenesis and stimulate vasculogenesis in primary cultures of microvascular endothelial cells (MVECs) from neonatal rat mesentery. Isolation, purification, characterization, and culture of MVECs were performed. Cell proliferative effects of rhEpo were studied by 3-(4,5 dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay in cultured MVECs. Vasculogenic effects of rhEpo were examined on cultured MVECs plated on either hormone-rich Matrigel substratum or the extracellular matrix protein, type I collagen. Our findings show that MVECs are isolated and purified, and that rhEpo stimulates MVEC proliferation, with maximal proliferation seen with a concentration of 50 IU/mL rhEpo. Tubule formation assays reveal that an rhEpo concentration of 50 IU/mL produces maximal tubule formation after 12 h on both Matrigel and the simple substratum, type I collagen. Our study is the first to examine the effects of rhEpo on the endothelium of the neonatal gastrointestinal tract. These data suggest that Epo may have a trophic effect on the vasculature of the gastrointestinal tract early in development. Furthermore, as Epo has been measured in breast milk, and its receptor has been shown to exist on the mucosa and gastrointestinal vasculature, Epo may be an endogenous stimulant of vessel growth during neonatal gastrointestinal development.