Amyloidosis as an incidental finding in rats on experiment.

Abstract

In a review paper (Dunn, 1967) on amyloidosis in laboratory animals, covering both the spontaneous and experimentally-produced disease, it was stated that rats seldom suffer from spontaneous amyloidosis, and that attempts to produce the condition had failed. This is puzzling, as it is commonly seen in mice and is not infrequently found in guinea-pigs, rabbits and hamsters. There is no reason to suppose that rats are any less susceptible to chronic inflammatory processes than other laboratory species. It was therefore of considerable interest when amyloid was encountered in rats which had been used for simple radiographic studies. Deposits were found in all organs which were examined histologically; they were strongly stained with congo-red and exhibited bright green birefringence when examined with polarised light. Confirmation by electron microscopy was not attempted. The animals were from a conventional Sprague-Dawley rat colony known to suffer from chronic respiratory disease with characteristic lesions in the lung. Both Mycoplasma pulmonis and Bordatella bronchiseptica were recovered from the upper respiratory tract and lungs, whilst significant antibody levels to Sendai virus were consistently demonstrated in individual serum samples. The radiographic study (Kreel, Green & Tavill, 1972) entailed immobilising rats by intramuscular injection of 0·05 mljlOO g bodyweight fentanyl-haloanisone ('Hypnorm'; Crown Chemicals Ltd, Lamberhurst, Kent) followed by intravenous injection via the penile vein of 1·2 ml of radio-contrast medium ('Urovision', a mixture of sodium amidotrizoate and meglumine amidotrizoate; Schering A.G., Berlin). Several angiograms and a pyelogram were taken. This was repeated over a period of 6 days.