Purification and characterisation of two porcine hypothalamic fractions with LH-releasing activity: evidence for a single LH and FSH-releasing hormone.

Two fractions with LH releasing activity were obtained from porcine hypothalami by Enzmann et al. (1972). These fractions were designated E 57 and E 203. By comparison with pure natural LH-RH and synthetic LH-RH, E 203 was identified as purified natural LH-RH. E 57, which has only 25% of the activity of E 203, was further evaluated for its biological and immunological activity. E 57 has the same ratio of LH/FSH-releasing activity as natural LH-RH. The binding to a specific LH-RH antiserum is identical with that of natural LH-RH and E 203. It is concluded, that E 57 is an artifact of isolation derived from natural LH-RH. These findings can be considered as additional evidence for the identity of the hypothalamic LH and FSH releasing hormone, since both gonadotrophins are stimulated by the two hypothalamic fractions.