Pro-opiocortin peptides in rat cerebrospinal fluid

Cerebrospinal fluid (CSF) taken from rats implanted with chronic cisternal cannulae was subjected to gel filtration chromatography on Sephadex G-50. Fractions were monitored using radioimmunoassays for N-terminal pro-opiocortin (N-POC), gamma 3-melanotropin (gamma 3-MSH), C-terminal adrenocorticotropin (C-ACTH), alpha-endorphin, beta-endorphin, gamma-lipotropin (gamma-LPH) and alpha-MSH. Two peaks which corresponded in elution position to rat N-POC (1-74) and gamma 3-MSH were detected. The major C-ACTH-immunoreactive (IR) peak was found to correspond to 14k ACTH. While no alpha-endorphin immunoreactivity was detected in rat CSF, three beta-endorphin-IR peaks were identified in positions expected for beta-LPH, beta-endorphin (1-31) and beta-endorphin (1-27), as well as a major peak of activity with the elution characteristics and cross-reactivity of rat gamma-LPH. HPLC of the alpha-MSH-IR material in rat CSF revealed the presence of a major peak of immunoreactivity whose retention time did not correspond to the known oxidised and reduced forms of alpha-MSH and its desacetylated and diacetylated derivatives. The identity of this peak is unknown.