INTESTINAL UPTAKE AND ORGAN DISTRIBUTION OF IMMUNOMODULATORY AMINATEDBETA-1,3-D-POLYGLUCOSE IN ATLANTIC SALMON (SALMO-SALAR L)

Intestinal uptake and organ distribution of aminated beta-1,3-D-polygl ucose (AG), a potent soluble immunomodulator, were studied in the Atla ntic salmon (Salmo salar L.). AG was tritiated or labelled with I-125- tyramine cellobiose and traced after intravenous injection (I-125-TC-A G), or after intragastric or rectal administration (I-125-TC-AG or [H- 3]AG) to the Atlantic salmon. Plasma levels and tissue distribution of AG were investigated. AG appeared in blood and various tissues within minutes after rectal or intragastric administration. Histological inv estigations showed that fluorescence-labelled AG was taken up by epith elial cells in the lower part of the intestine. Blood clearance of int ravenously injected I-125-TC-AG was rapid; about 50% of the labelled A G had disappeared from blood after 20 min. The highest amounts of radi olabelled AG following intravenous injection were found in liver, sple en and kidney. Radioactivity per g tissue was equal in head and trunk kidney. Significant amounts of radioactivity were also found in the wa ll of the hindgut after intestinal administration. The fact that amina ted beta-1,3-D-polyglucose is transported through epithelial cells in the intestine and cleared from the blood in lymphoid tissues suggests the possible use of this immunomodulating polysaccharide as feed addit ive in fish culture.