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Extraction of Cartilage Sulfation Inhibitors and Somatomedins from Rat Liver^*

Section of Endocrinology, Department of Medicine, The University of Texas M. D. Anderson Hospital and Tumor Institute at Houston Houston, Texas 77030

Address all correspondence and requests for reprints to: R. Vassilopoulou-Sellin, M.D., Section of Endocrinology, The University of Texas M. D. Anderson Hospital and Tumor Institute at Houston, 6723 Bertner Avenue, Houston, Texas 77030.

Abstract

Both cartilage sulfation inhibitors and somatomedins were identified in extracts from rat liver. After extraction at pH 7.4 (neutral extract), cartilage inhibitors were found in neutral liver extracts from normal, diabetic, fasted, and hypophysectomized rats [61 ± 4%, 68 ± 3% 60 ± 6%, and 62 ± 7% below assay buffer (mean ± SEM), respectively; all P < 0.001 below buffer]. Exposure to 80 C or pH 2.4, inactivated the inhibitors in all samples. After gel filtration on Sephadex G-100, pH 7.4, cartilage inhibitors in the neutral extracts had molecular sizes similar to those of inhibitors in the diabetic rat serum (mol wt, >45,000). After the inhibitors were removed with neutral buffer extraction, reextraction at pH 2.4 (neutral/acid extracts) revealed somatomedins only in the livers of normal rats. Cartilage stimulation by somatomedins in neutral/acid extracts was linear and parallel to stimulation by normal serum. After gel filtration on Sephadex G-75, pH 2.4, somatomedins in neutral/acid extracts from normal rat liver were found to have an apparent molecular weight larger than that of serum somatomedins (mol wt, 25,000–45,000), consistent with recent findings for hepatic somatomedins. The data indicate that both somatomedins and inhibitors can be extracted from rat liver. (Endocrinology 114: 576, 1984)

Footnotes

^* This work was supported by Grants CA-05831-20 and CA-27612-03 awarded by the NCI, NIH, and the Nancy Carmichael Gift Funds.

Received January 3, 1983.