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Part of the hyaluronic acid (HA) synthesized in peripheral tissues enters the blood circulation through the lymph. It is rapidly taken up by the endothelial cells in the liver (half-life in blood is 2.5-5.5 minutes) and degraded. Pure primary cultures of liver endothelial cells were obtained by a newly developed technique and used to follow the metabolism of the polysaccharide on the cell surface. At 37 degrees C the HA is effectively endocytosed and degraded to acetate and lactate. A radioassay specific for HA and sensitive in the nanogram range has been developed to follow the concentration of HA in serum. The normal level in man is 10 to 100 micrograms/l. Elevated serum levels of HA are seen in liver cirrhosis, rheumatoid arthritis and scleroderma indicating that both an impaired catabolism in the liver and an increased synthesis in the peripheral tissues can modify the HA level.

Profilactin and profilin have been purified from calf thymus and calf brain. Thymus profilactin could be crystallized with a similar technique as described earlier for the spleen protein. Preparations of profilactin from the three calf tissues spleen, thymus and brain contain a mixture of β actin and γ actin. The ratio β/γ differs between the tissues, but is constant throughout the purification steps. The properties of profilin isolated from three sources (spleen, thymus and brain) indicate that it is a highly conserved protein.

A one step procedure, consisting of affinity chromatography, was worked out for the purification from crude extracts of calf thymus of the protein inhibitor specific for pancreatic deoxyribonuclease (DNAase I).For this purpose DNAase I was immobilized on agarose. This solid phase enzyme conjugate was shown to have the ability to adsorb from crude extracts one major protein, which could be eluted again with 3 M guanidine-HC1 in 1 .OM sodium acetate and 30 glycerol. This protein preparation had only a little DNAase inhibiting activity, but could be identified by gel electrophoresis and peptide mapping as the inhibitor protein described recently. The low recovery of inhibitor activity was due to poor stability of the inhibitor protein in the solvent system found necessary to effect its elution from the column material.So far nothing is known about the precise function(s) of the proteinaceous DNAase inhibitor occurring abundantly in mammalian tissues (for references see [l]). We have reported earlier [l] that as much as 5-100/, of the soluble protein from thymus cells consists of this inhibitor. A protein that is present in such a high amount in the cell must, as we see it, occupy it central position also from a functional point of view.Recently we started a series of experiments trying to find out when in the life cycle of the mammalian cell this protein is synthesized. It became clear however, even in the beginning of these studies, that it would not be possible to obtain unambigous results by resorting only to studies of the inhibitor activity, but that we had to measure the actual synthesis of the inhibitor protein by following the incorporation of labeled amino acids into it. Therefore we decided to develop a method by which we could prepare the inhibitor protein in one or a few steps free from contaminating proteins.Precipitating antibody techniques have been used for similar studies by others [2]. We have failed so far, however, in obtaining good antibody responses using the purified DNAase inhibitor and therefore we turned to affinity chromatography as an alternative to achieve the same result. This paper The results presented here corroborate earlier findings [l] that this inhibitor protein is one of the major protein components of the soluble part of the thymus cells. MATERIALS AND METHODS MaterialsThymus glands were obtained and stored as described elsewhere El].DNAase I once crystallized, from bovine pancreas (Sigma Chem. Co.) was used without further purification. Substrate DNA (highly polymerized, type I, Sigma) was prepared and the DNAase and DNAaseinhibitor activities were analyzed as described earlier Guanidine hydrochloride (grade Ultrapure) was purchased from Mann Research Laboratories. This material could be used without recrystallization.NP 40, nonionic detergent, was obtained from Shell Chemical Co.[1,51. Preparation of DNAase Substituted Xephurose"Activation" of Sepharose (Sepharose 4B, Pharmacia, Uppsala, Sweden) with CNBr [3,4] was performed as described in detail by Kato and Adinsen [el.The...