Introduction
Endotoxin (lipopolysaccharide from cell membranes of gram-negative bacteria) is often used to produce models of septic shock in animals. During septic shock, with hypotension, peripheral vasodilation and oedemaformation, the flux of macromolecules and fluid from plasma to the tissues is greatly enhanced. The oedema formation could be caused by increased permeability and/or increased capillary net filtration pressure. Intradermal injections of LPS cause increased vascular permeability (Ueno et al. (1996)) and a lowering of the interstitial fluid pressure. We have investigated the amount of albumin leakage after intravenous injection of two different preparations of LPS.
Methods
Female Wistar Møller rats weighing 200-250 grams, were anaesthetised with pentobarbital sodium. Lipopolysaccharide from Escherichia coli (serotype 0127:B8 and 0111:B4) was used in doses that caused the same level of hypotension (arterial pressure of about 40 mmHg). Two experimental groups, and one control group were studied (n=8 in each group). Group 1 received 0.3 mg/kg LPS (0111:B4), Group 2 received 0.15 mg/kg LPS (0127:B8). Controls received 0.4 ml saline. Five min after anaesthesia the rats received the test substance i.v.. Five min thereafter they received I125 (0.05 Mbq), which circulated for 55 min before I131 (0.05 Mbq) was injected i.v.. Five min later, the rats were killed with saturated KCl, blood samples were obtained, and tissue samples from the skin, small intestine and biceps femoris muscle were obtained. Albumin extravasation was calculated as the difference between the plasma equivalent distribution volume of I125 and that of I131-HSA. All calculations were referenced to dry tissue weight. Total tissue water in tissue samples was estimated as water content per gram of dry tissue weight.
Results
Group 2 had a significantly larger extravasation of albumin in all organs compared to both Group 1 and control (p<0.05) while there was no difference between Group 1 and Control.
Albuminextravasation in the skin on the paw and the back as well as in the biceps femoris muscle and intestine was increased in Group 2 compared to Group 1 and Control ( p<0.05). TTW was not different between the group the two experimental groups and control for any organ (p>0.05).
Conclusions
The type of capillary endothelium and the transcapillary fluid flux would be major factors influencing our results. We have previously described a lowering of interstitial fluid pressure after intravenous injections of LPS (Nedrebo et al. (1999)). These results show that the same serotype of LPS, in doses causing severe hypotension, also causes a significant increase of albumin from the circulation and into the interstitium, but with a significant difference between the two serotypes of LPS despite the fact that they resulted in the same degree of hypotension. The strain of LPS which caused a lowering of the interstitial fluid pressure, also caused increased extravasation of albumin.
References
Ueno,A., Tokumasu,T., Naraba,H. & Oh-ishi S. 1996. Jpn. J. Pharmacol. 70, 285-290.
Nedrebo,T., Berg, A. & Reed,R.K. 1999. Am.J.Physiol. 277, H1857-H1862.