Simultaneous Orcadian Variations of Plasma ACTH, Beta-Lipotropin, Beta-Endorphin and Cortisol

Abstract

The major objective of this study was to investigate the analogy existing between the typical circadian periodicity of ACTH and that recently described of β-lipotropin (β-LPH) and β-endorphin (β-EP) plasma levels. The determination of their concentrations, plus cortisol, has been performed on the same plasma samples of 6 healthy volunteers. All hormones were measured by radioimmunoassay. Those of β-LPH and β-EP were preceded by a purification of plasma through silicic acid extraction and Sephadex G-75 gel filtration. The highest values (mean ± SEM) were found in the morning (ACTH: 10.3 ± 0.9; β-LPH: 6.3 ± 0.7; β-EP: 6.5 ± 0.5 fmol/ml; cortisol: 378 ± 30 pmol/ml) and the lowest values in the evening (ACTH: 6.1 ± 0.7; β-LPH: 3.3 ± 0.4; β-EP: 3.7 ± 0.6 fmol/ml; cortisol: 130 ± 23 pmol/ml). Statistical analysis using the Fourier method led to the evidence of a concomitant circadian secretory pattern of the three proopiocortin-related peptides. These results strongly suggest that the phasic secretion of ACTH, β-LPH and β-EP underlies a common central control.