Porcine follitropin. Isolation and characterization of the native hormone and its alpha and beta subunits.

The properties of porcine follitropin and its subunits which have not yet been characterized are presented. The porcine follitropin obtained has a biological potency of 81 times the National Institutes of Health Porcine Follitropin P-1 preparation. Its contamination by lutropin and thyrotropin amounted to 1 and 0.5 percent by weight respectively, as measured by radioimmunoassay. The alpha and beta subunits of porcine follitropin were obtained by incubation in an acidic urea solution followed by anion exchange chromatography. The amino acid composition of porcine follitropin alpha subunit was found to be identical to that of alpha chain of porcine lutropin and thyrotropin. These porcine alpha chains differ, nevertheless, markedly in their carbohydrate composition particularly with respect to their mannose and galactose contents. The amino-terminal residue of the follitropin alpha subunit is threonyl. The carboxy-terminal end of the alpha chain is of variable length. Cysteyl residue was detected at the aminoterminal end of the follitropin beta chain with glutamic acid at its carboxy-terminal end. Cross-contamination of the alpha and beta subunit preparations was measured by specific radioimmunoassay and amounted to 0.5 and 0.1 percent by weight respectively.