Experimental amyloidosis induced by saponin.

White male rabbits, weighing about 3 kg, were injected intravenously with 5 ml of 0.1% saponin solution dissolved in physiological saline once a week for six months. The sequential histological changes in the kidneys were observed by repeated biopsies and, in addition, the animals were subjected to necropsy for light and electron microscopic examinations. Amyloid protein was purified from the animal tissues, estimated at approximately 6,300 daltons in molecular weight by SDS-PAGE and considered as an AA type protein based on its amino acid sequence study. The antibody against the purified amyloid protein was produced in guinea pigs and was used for immunohistochemical studies. The deposition of amyloid started initially in mesangial matrices and subendothelial regions of the glomeruli, but at the end the spleen, kidney and bowels were found to be frequent sites of deposition. The amyloid deposited in the tissues was specifically positive by the indirect immunohistochemistry using the prepared antibody. This antibody also reacted positively to human materials with secondary amyloidosis. These results indicate that amyloidosis induced by saponin is a good model of secondary amyloidosis.