Endotoxin impedes vasoconstriction in the spleen: role of endogenous interleukin-1 and sympathetic innervation.

Processes relevant for an appropriate immune response such as immune cell traffic and recirculation require a tight control of blood supply to lymphoid organs. Interactions between endogenous cytokines and sympathetic nerve fibers in lymphoid organs can contribute to this control. The results reported in this paper show that 1) administration of low doses of lipopolysaccharide (LPS), an endotoxin derived from gram-negative bacteria, causes an increase in splenic blood flow (SBF); 2) this increase is mediated by the production of endogenous interleukin-1 (IL-1); 3) the effect of LPS on SBF requires an intact splenic sympathetic innervation; 4) the LPS-induced increase in SBF is exerted at the postganglionic level; 5) the endotoxin inhibits the vasoconstriction induced by the in vivo stimulation of the splenic nerve but does not affect the vasoconstriction induced by norepinephrine (NE); and 6) although IL-1 and LPS stimulate general sympathetic activity as reflected by increased peripheral vascular resistance, they do not increase NE concentration in splenic dialysates. Together these in vivo results indicate that endogenous IL-1 affects blood supply to the spleen by inhibiting the sympathetic vasoconstrictor tonus at a postganglionic, prejunctional level. This effect is expected to be relevant for immune cell recirculation, homing, and traffic as well as antigen trapping in the spleen, an organ specialized in the control of these processes during immune responses.

Physiological studies of exocrine pancreatic secretion in conscious rats. 1. Communication: surgical methods and registration techniques.

1. Two surgical methods are described to derive bile and pancreatic juice separately by indwelling catheters in rats. 2. The secretes are always recirculated into the animals duodenum, the indwelling catheters forming an extracorporal loop. 3. The experiments are performed in the conscious animal. 4. The flow rate of the secretes is measured by drop-counting with resetting after a definite number of drops (staircase registration). 5. By interposed flow-through transducers several parameters can be determined f. i. by ion-selective-electrodes and microphotometers. 6. Additional analytic measurements can be carried out in samples. 7. There is a time-shift between the recorded curves corresponding to several different flow-through transducers placed one after the other in the extracorporal circuit of flow. This time shift is variable due to the dead spaces of the system and the actual flow-rate. The theoretical aspects of this general problem are discussed in detail. 8. Sampling of pancreatic juice causes immediately a pronounced increase of flow rate and the amount of protein secreted. Therefore, volumes taken must be given back quantitatively into the animals duodenum in order to avoid a disturbance of the normal secretion pattern.