The effect of alpha-adrenergic antagonism upon nitrogen loss during endotoxemia

The effect of sepsis during parenteral nutrition on hepatic microsomal function in rats

STUDY OBJECTIVE

To investigate the effect of sepsis during parenteral nutrition on hepatic cytochrome P450 (CYP) activity in rats.

DESIGN

Prospective, randomized, controlled study.

SETTING

University-based animal research laboratory.

ANIMALS

Twenty adult male Sprague-Dawley rats.

INTERVENTION

The animals were cannulated intravenously and randomized to receive parenteral nutrition (PN), intravenous live Escherichia coli 4 x 10(8) colony-forming units/100 g body weight for 2 consecutive days with PN (PNEC), or chow (CH).

MEASUREMENTS AND MAIN RESULTS

Both PN alone and PNEC resulted in a progressive decline in hepatic CYP concentration compared with CH (0.53 +/- 0.10, 0.41 +/- 0.17, and 0.35 +/- 0.14 nmol/mg microsomal protein, respectively, p < 0.05). Parenteral nutrition alone was associated with a 57% decrease in isoenzyme ethoxycoumarin-O-deethylase activity (ECOD) compared with CH, but sepsis did not further decrease ECOD activity any more than PN alone (0.103 +/- 0.049, 0.044 +/- 0.018, and 0.050 +/- 0.020 nmol/mg microsomal protein/min, respectively, p < 0.05).

CONCLUSION

Hepatic CYP concentration declines with PN and is further decreased when compounded by sepsis. The disproportional decrease in ECOD activity relative to CYP concentration with PN is unchanged by sepsis, indicating a selective alteration in hepatic isoenzymes by PN.

Endotoxin-mediated hepatic lipid accumulation during parenteral nutrition in rats

OBJECTIVE

To assess the effect of endotoxemia on hepatic lipid content during parenteral nutrition (PN) in rats.

METHODS

Twenty male Sprague-Dawley rats (185-230 gm) were randomized to receive PN (n=9) or PN plus a continuous infusion of E. coli 026:B6 lipopolysaccharide (LPS; n= 11). All animals received isocaloric (170 kcal/kg/day), isonitrogenous (1.1 g N/kg/day), glucose-based PN for the next 78 hours. After 30 hours of adaptation to TPN, the animals were randomized to receive PN or PN plus LPS at 6 mg/kg/day for the remaining 48 hours of study. The animals were euthanized and the livers were harvested.

RESULTS

Liver weight increased significantly (by 60%) from 7.5+/-0.6 g to 12.1+/-2.4 g (p < or = 0.01) in the animals who received PN versus LPS, respectively. The proportion of liver water remained the same for PN and LPS groups (72.9+/-3.2% versus 72.3+/-3.8%, respectively, p = N.S.). However, liver fat increased disproportionately (by about 130%) from 0.20+/-0.05 g to 0.46+/-0.20 g (p < or = 0.01) total fat weight or from 9.6+/-1.8% to 13.6+/-4.1% (p < or = 0.02) lipid content (g/g) of the dry liver weight for the PN and LPS groups, respectively.

CONCLUSION

Endotoxin, when given concomitantly with parenteral nutrition, increases hepatic lipid accumulation and thus augments the development of parenteral nutrition-associated fatty liver in rats.

Effect of pentoxifylline on nitrogen balance and 3-methylhistidine excretion in parenterally fed endotoxemic rats

Pentoxifylline interrupts early gene activation for tumor necrosis factor, interleukin-1, and interleukin-6 production and improves survival from experimental sepsis. These effects can alter nitrogen loss during critical illness. To determine the dose-dependent influence of pentoxifylline on nitrogen loss, 44 male Sprague-Dawley rats (220 to 265 g) were randomized to receive parenteral nutrition only (PN), PN plus continuous infusion of Escherichia coli 026:B6 lipopolysaccharide (LPS) at 9 mg x kg(-1) x d(-1), or PN plus LPS plus a continuous infusion of pentoxifylline at either 25 (PEN25) or 100 mg x kg(-1) x d(-1) (PEN100) for 48 h. Before randomization, all animals underwent intravenous cannulation and 40 h of PN adaptation. All animals received isocaloric, isonitrogenous PN (160 kcal x kg(-1) x d(-1) and 1.0 gN x kg(-1) x d(-1)) and were kept nil per os except for water ad libitum. Administration of LPS significantly worsened nitrogen balance for all three groups compared with PN control; however, pentoxifylline only modestly improved nitrogen balance compared with LPS (206 +/- 255, -497 +/- 331, -332 +/- 329, and -310 +/- 383 mg/48hr for the PN, LPS, PEN25, and PEN100 groups, respectively; P < 0.001). Pentoxifylline did not significantly change 3-methylhistidine urinary excretion compared with LPS (573 +/- 180, 705 +/- 156, 780 +/- 326, and 683 +/- 266 microg/48 h for the PN, LPS, PEN25, and PEN100 groups, respectively, P not significant). Pentoxifylline, given in therapeutic doses after an endotoxin challenge, modestly, but not significantly, improved nitrogen balance. Urinary 3-methylhistidine excretion was not influenced by pentoxifylline. A dose-dependent effect by pentoxifylline on these markers was not evident.