Biliary obstruction exacerbates the hepatic microvascular inflammatory response to endotoxin.

Gram-negative sepsis is a serious complication for patients with obstructive jaundice. The present study was conducted to elucidate the response of hepatic microcirculation to endotoxin 2 weeks after bile duct ligation (BDL) or sham-operation in rats. Two hours after lipopolysaccharide (LPS) injection (1, 10, or 100 microg/kg, iv.), the hepatic microvasculature was examined using in vivo microscopy. BDL elicited increases in leukocytes adhering to the sinusoidal wall, swelling of sinusoidal endothelial cells as well as phagocytic activity of hepatic macrophages and a decrease in the numbers of perfused sinusoids. LPS (1, 10, 100 microg/kg) further increased leukocyte adhesion and reduced the numbers of perfused sinusoids in a dose-dependent manner. Leukocyte adhesion in response to LPS (1, 10, 100 microg/kg) in BDL rats was increased 6.1-fold, 5.9-fold, and 3.3-fold, respectively when compared with sham-operated rats. The numbers of perfused sinusoids in response to LPS (1, 10, 100 microg/kg) in BDL rats were decreased by 42%, 36%, and 45%. While 1 and 10 microg/kg LPS also elicited an increase in phagocytic activity in BDL rats when compared with sham-operated rats, the response to 100 microg/kg LPS was suppressed. LPS did not affect the numbers of swollen endothelial cell in BDL rats. The present study demonstrated that chronic biliary obstruction enhanced the hepatic microvascular response to low doses of endotoxin. This observation suggests that exaggerated hepatic microcirculatory dysfunction during sepsis contributes to the development of liver injury and a high incidence of morbidity and mortality in biliary obstruction.

High doses of intravenous immunoglobulin G enhance Kupffer cell phagocytic function during the late phase of sepsis and endotoxemia in rats.

The effect of intravenous immunoglobuln G (ivIG) on the hepatic microvascular inflammatory response during the late phase of sepsis and endotoxemia in rats was studied by using in vivo microscopy. One hour after administration of a clinically relevant dose of ivIG (0.5 g/kg body weight, Sandoglobulin), rats were subjected to polymicrobial sepsis induced by cecal ligation and puncture (CLP) or were injected intravenously with lipopolysaccharide (LPS, 0.1 mg/kg body weight). Twenty-four hours after CLP or LPS, the number of leukocytes adhering to the sinusoidal wall was increased 11.0-fold in CLP-treated animals and 5.6-fold in LPS-treated animals, respectively, compared with the controls. Concomitantly, the numbers of swollen sinusoidal endothelial cells were increased 4.2-fold and 3.2-fold. The number of perfused sinusoids was decreased by 35% and by 24%. These responses were minimized by pretreatment with high doses of ivIG. Kupffer cell phagocytic activity in the periportal sinusoids in CLP-treated animals was decreased by 41%, whereas that in the centrilobular sinusoids in LPS-treated animals was increased by 72%. IvIG significantly elevated this activity in both CLP- and LPS-treated animals and the number of ED2-positive Kupffer cells in tissue sections. The results suggest that ivIG limits the hepatic microvascular inflammatory response during the late phase of sepsis and endotoxemia by affecting Kupffer cell function.

Effect of intravenous immunoglobulin G on the TNFalpha-mediated hepatic microvascular inflammatory response.

The effect of intravenous immunoglobulin G (ivIG) on the hepatic microvascular inflammatory response elicited by tumor necrosis factor alpha (TNFalpha) in rats was studied by means of in vivo microscopy and histological examination. One hour after the portal infusion of TNFalpha, the average number of leukocytes adhering to the sinusoidal endothelium was increased sevenfold, and the average number of the perfused sinusoids was decreased by 15% when compared with controls. Concomitantly, the expression of intercellular adhesion molecule-1 (ICAM-1) on the hepatic sinusoidal endothelium and that of the central vein was increased. The phagocytic activity of Kupffer cells in centrilobular sinusoids was increased by 54%, as were the number of ED2-positive Kupffer cells in tissue sections. Pretreatment with a clinically relevant high dose of ivIG (1 g/kg body weight, Sandoglobulin) minimized these responses by reducing leukocyte-endothelial interactions and Kupffer cell phagocytic function. The results suggest that high doses of ivIG limit the hepatic microvascular inflammatory response by inhibiting the action of the proinflammatory cytokine TNFalpha.

Infusion of a pineal gland-derived antigonadotropic decapeptide into the lateral ventricle depresses prolactin levels in male rats.

The primary structure of a pineal gland-derived antigonadotropic decapeptide (AGD) was determined recently, and a synthetic analog prepared by solid state methods. Adult male Harlan SD rats were maintained under controlled photoperiods. Each was fitted stereotaxically with a stainless steel cannula for infusion into a right lateral ventricle. Each cannula was attached to a subcutaneous osmotic minipump filled either with artificial cerebrospinal fluid (CSF) or the AGD in CSF (0.5 micrograms/microliters). Additional Tygon microbore cannulae were inserted through the femoral artery and placed in the abdominal aorta for blood sampling and the determination of prolactin (PRL) levels by radioimmunoassay. CSF (1.0 microliter/hr) or the AGD (0.5 microgram/hr) was infused into the right lateral ventricle over a period of seven days. Circulating PRL concentrations were significantly depressed by AGD infusion both in the morning and late afternoon; adenohypophysial concentrations were concomitantly elevated on infusion day seven. These results confirm previous observations of inhibitory effects of the AGD on PRL secretion, and further support its postulated central mechanism of action.

Immunoreactive inhibin decreases following bilateral ovariectomy and during the postovulatory rise of FSH in Syrian hamsters.

Inhibin is a heterodimeric glycoprotein which may regulate FSH synthesis and secretion as well as follicular development and maturation. The source and physiological role of inhibin have not been established for the hamster, although several investigators have suggested that this hormone may function in the regulation of FSH in this species. The major objectives of the present studies were to develop a radioimmunoassay (RIA) for the measurement of inhibin in hamster serum and tissue, to identify the primary source of inhibin and to examine the relationship between inhibin and FSH during the estrous cycle. A sensitive, accurate and specific RIA was developed and utilized to measure changes in circulating levels of immunoreactive inhibin (ir-inh-alpha) following bilateral gonadectomy and throughout the estrous cycle. Circulating ir-inh-alpha declined rapidly and significantly following bilateral gonadectomy in female hamsters suggesting a gonadal source. Serum FSH concentrations increased following the decline in serum ir-inh-alpha levels. In the adult female hamster circulating ir-inh-alpha increased gradually throughout diestrus, peaked at the time of the preovulatory gonadotropin surge, then declined to a nadir on the morning of estrus. Changes in ovarian inhibin subunit mRNAs were examined throughout the estrous cycle and correlated with changes observed in circulating ir-inh-alpha levels. Observed significant reductions in the relative amount of inhibin mRNAs and serum concentrations of ir-inh-alpha during early estrus may moderate the amount and duration of the secondary FSH rise and thus contribute to the regulation of follicle recruitment in the hamster.

Chronic lateral ventricle infusion of a pineal gland-derived decapeptide alters pulsatile secretion of LH in rats.

The object of this investigation was to determine whether chronic lateral ventricle infusion of a pineal gland-derived antigonadotropic decapeptide (AGD) would affect pulsatile luteinizing hormone (LH) release in conscious, unrestrained male rats. Adult male Harlan SD rats were bilaterally orchiectomized and maintained under conditions of controlled photoperiods and temperature. After three (Experiment one) or four (Experiment two) weeks each was fitted stereotaxically with a stainless steel cannula for infusion into the right lateral ventricle. Each cannula was attached to a subcutaneous osmotic minipump filled either with artificial cerebrospinal fluid (CSF) or AGD in CSF (0.5 microgram/microliter). CSF (1.0 microliter/hr) or the AGD (0.5 microgram/microliter hr) was infused over a period of four days. Blood samples for determined of LH by radioimmunoassay were obtained at five minute intervals from a Tygon microbore cannula inserted via a femoral artery into the abdominal aorta. LH pulses were defined and identified with a computerized deconvolution algorithm designed to determine spontaneous LH secretory events. Although mean LH levels were not significantly reduced, LH secretory pulse frequency and nadirs were significantly decreased by ADG infusion (p<0.01). Additionally, LH secretory pulse amplitude and LH secretory response to LHRL administration were significantly increased (p<0.01) by AGD treatment. These results confirm initial reports of depressive effects of the AGD on LH secretion and support its hypothesized central site of action.

Artificial formula induces precocious maturation of the small intestine of artificially reared suckling rats.

BACKGROUND: The artificially reared rat model was used successfully to study the effect of nutrition during the early postnatal period on growth and development of the neonate. Overgrowth and morphologic changes of the gastrointestinal tract are known consequences of artificial rearing. The major goal of our study was to elucidate whether artificial rearing-enhanced gut development is caused by artificial diet or by gastrostomy and the artificial rearing technique itself. METHODS: Suckling rats at day 8 of age underwent intragastric cannulation and were machine fed either a cow's milk-based artificial rat's milk substitute or pooled rat's milk for 4 days. Dam-fed littermates served as a control. RESULTS: Body growth did not differ in the three experimental groups. In rats receiving rat's milk substitute, small intestinal wet weight was approximately 60% greater than in rats fed rat's milk or control rats. Additionally, the entire small intestine was approximately 20% longer in the rat's milk substitute group. Morphologically, rat's milk substitute-fed pups demonstrated significantly greater intestinal villus length and crypt depth compared with rat's milk-fed or control rats. Jejunum and midjejunum of the rat's milk and control groups did not differ in these parameters. Intestinal sucrase activity of rat's milk substitute-fed rats was significantly elevated compared with rat's milk-fed rats or control animals. CONCLUSIONS: These results indicate that cow's milk-based formula, not gastrostomy or artificial feeding technique, is a principal cause of the small intestine overgrowth and precocious maturation of some intestinal functions observed in artificially reared sucklings.