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binding isotherm in a single experiment. Both preparations contained a saturable component able to bind glycocholic acid although the number of sites in the ileal preparation (179pmol/g of supernatant protein) was greater than that in the jejunal preparation (47,umol/g of supernatant protein). The similarity between the value for the dissociation constant of the ileal component (2.5pmol/l) and that of the jejunal component (1.6pmoI/l) suggests that it may be the same component that is present in different concentrations in both preparations. Previous studies identified two proteins in liver supernatants able to bind bile acids. Both these proteins possessed glutathione S-transferase activity and one was provisionally identified as the non-specific anion-binding protein ligandin (glutathione S-transferase B) (Strange et al., 19776). In contrast with the bile-acid-binding proteins found in liver, the binding component of mol.wt. approx. 40000 found in the small intestine did not possess glutathione S-transferase activity and unlike ligandin was not retained by CM-Sephadex. The terminal ileum is quantitatively an important site of bile-acid transport and the function of the soluble protein may be to ensure that the intracellular concentration of free bile acid remains small.

centrifugation restored these increases when included in the heparin-containing medium at concentrations of 10-8Opg of protein/ml. The ability of heparin to stimulate the release of lipoprotein lipase from human adipose tissue in vitro has been demonstrated by several groups of workers (Elkeles, 1974). That this release can be closely correlated with triacylglycerol clearance provided further evidence of the central role played by this enzyme in the transfer of triacylglycerol from blood to peripheral tissues. Serum lipoproteins appear to have a role in potentiating the release of the enzyme from the tissue.