Lysosomal enzyme activities in sheep plasma and lymph

The activities of acid phosphatase, beta-glucuronidase and N-acetyl-beta-glucosaminidase were measured in blood plasma, afferent and efferent popliteal lymph, intestinal lymph and in four different organs of the sheep. Acid phosphatase had an optimum activity at pH 4-5 while beta-glucuronidase and N-acetyl-beta-glucosaminidase had optimal activities at pH 5-0 and pH 4-5-5-0, respectively. Comparative studies showed that the sheep had very low activities of acid phosphatase and relatively low activities of N-acetyl-beta-glucosaminidase in the blood plasma compartment in relation to the activities of these enzymes in the plasma of the rabbit and the rat. The tissue activities of all three enzymes were relatively high when compared with those in the two non-ruminant species. It is considered that the low plasma activities of acid phosphatase in the sheep reflect a rapid turnover of this enzyme in the plasma compartment. The activities of the three enzymes in regional lymph indicated that acid phosphatase was being added to the capillary filtrate at a regional tissue level, whereas beta-glucuronidase and N-acetyl-beta-glucosaminidase in lymph were derived from filtration from the blood plasma compartment on a molecular weight basis. The high lymph: plasma ratios observed for acid phosphatase activity in intestinal lymph may indicate a function of this enzyme in lipid absorption in the sheep.