BINDING-INHIBITORY AND GROWTH-INHIBITORY EFFECT OF HEPARIN AND OLIGO-HEPARIN (2-KDA) IN BALB C 3T3 CELLS - LACK OF EFFECT ON PDGF-INDUCED OR SERUM-INDUCED INOSITOL LIPID TURNOVER/

1 The ability of heparins (bovine heparin sm 1026, Av. mol. wt. 36.9 k Da and bovine heparin EP 756, Av. mol. wt. 12.9 kDa) and heparin fract ions of different molecular weights (low molecular weight heparin, LMW 2123/OP, Av. mol. wt. 4.5 kDa and oligo-heparin, Av. mol. wt. 2 kDa) to inhibit the proliferation and signalling of Balb/c 3T3 fibroblasts was investigated. 2 Heparin and heparin fractions of 4.5 and 2 kDa sig nificantly inhibited DNA synthesis as monitored by [H-3]-thymidine inc orporation. 3 H-3-labelled heparin fractions of 4.5 and 2 kDa were pre pared by gel-chromatography fractionation on Sephadex G-75 of an H-3-l abelled commercial heparin after treatment with heparinase. 4 The bind ing of unfractionated and oligo-heparin of 2 kDa to Balb/c 3T3 fibrobl asts was studied; we determined the specificity of heparin and oligo-h eparin binding to the cells by means of displacement of bound H-3-labe lled compound in response to increasing concentrations of unlabelled c ompounds. Scatchard analysis of binding data obtained using [H-3]-hepa rin as ligand revealed the presence of a single class of high affinity binding sites (K-d = 28 nM) for heparin. Scatchard analysis of bindin g data obtained using [H-3]-oligo-heparin as ligand revealed the prese nce of a single class of low affinity binding sites (K-d = 3.2 mu M) f or oligo-heparin. 5 In addition heparin displaced [H-3]-oligo-heparin at a concentration of approximately 100 fold of the K-d determined in displacement studies. Furthermore, oligo-heparin significantly displac ed [3H]-heparin at a concentration of approximately 10 fold of the K-d determined by displacement studies. 6 Both heparin and oligo-heparin exert their inhibitory effects on Balb/c 3T3 DNA synthesis stimulated by PDGF or serum. However these molecules did not affect the inositol lipid turnover triggered by PDGF at a concentration which did not prod uce maximal response. The increase of inositol phosphate metabolism pr oduced by 20% serum was also unaffected by heparin. This concentration of serum elicited a response comparable to that induced by a submaxim al concentration of PDGF.