KINETICS OF NITRIC-OXIDE SYNTHASE INDUCTION BY PROPIONIBACTERIUM-AVIDUM AND LIPOPOLYSACCHARIDE

Conditions for the induction of rat liver Ca2+-independent nitric oxid e synthase were determined with killed Propionibacterium avidum, and c ompared with lipopolysaccharide endotoxin. Similar maximal induction w as obtained intraperitoneally with the two types of inducers but kille d Propionibacterium avidum gave a long-lasting induction while lipopol ysaccharide displayed a rapid and short response. Moreover, the induct ion resulting from an intravenous administration of killed Propionibac terium avidum reached 60 times that of the control whereas lipopolysac charide treatment induced a 24-fold stimulation only. It is noteworthy that with the first inducer the nitric oxide activity was stable with time whereas with the second one it dropped after 8 h. Whatever the r oute of administration of killed Propionibacterium avidum, some huge v acuolated Kupffer cells were found in the liver whose parenchyma was a lmost normal. Numerous monocytes, and unaltered Kupffer cells, were ob served. Kupffer cells were identified to be responsible for the uptake of killed Propionibacterium avidum.