Histological and ultrastructural changes following carrageenan injection in the mouse.

Mice were injected intravenously with either uncharacterised potassium carrageenan or purified iota carrageenan and tissue was examined by light and electron microscopy 1 hr and 24 hr later. The survival of animals injected with these carrageenans was monitored over a 6-month period. Histological examination of liver and kidney was carried out on animals which died during this time and in the surviving mice at 28 weeks. Histological and ultrastructural evidence of disseminated intravascular coagulation was observed within 24 hr of carrageenan injection. The changes were more severe in animals given potassium carrageenan. Electro-microscopic examination of liver revealed carrageenan within membrane-bound vacuoles in Küpffer cells. These cells were largely unaffected by phagocytosis of iota carrageenan but uptake of potassium carrageenan resulted in marked ultrastructural changes and occasional damage to adjacent hepatocytes. Mice given potassium carrageenan had the poorer long-term survival and many animals in this group showed chronic renal damage with features which suggested obstructive nephropathy. A smaller proportion of mice injected with iota carrageenan displayed similar changes. There was no evidence of long-term hepatotoxicity in either group although both types of carrageenan persisted within liver macrophages for at least 6 months after injection.