Pulsatility of 24-hour concentrations of circulating interleukin-1-alpha in healthy women: analysis of integrated basal levels, discrete pulse properties, and correlation with simultaneous interleukin-2 concentrations.
Even though it is widely known that interleukin (IL)-1 alpha acts at the local level, it is still uncertain whether IL-1 alpha is secreted into the circulation and acts at distant sites. We have tried to elucidate this by measuring 24-hour levels of total IL-1 alpha in six healthy female volunteers. Subjects had detectable and pulsatile levels of IL-1 alpha throughout the 24-hour period. The integrated 24-hour IL-1 alpha concentration was 2,367 +/- 753 min x micrograms/l (mean +/- SD), and the integrated pulsatile IL-1 alpha concentration was 553 +/- 260 (25 +/- 10% ot total integrated IL-1 alpha). The mean IL-1 alpha concentration was 1.63 +/- 0.53 micrograms/l, mean pulse frequency/24 h was 12.8 +/- 0.8, mean pulse height was 2.31 +/- 0.52 micrograms/l; mean pulse width was 80.4 +/- 2.3 min, and mean interpulse interval was 105.3 +/- 2.8 min. Total IL-1 alpha levels significantly correlated with those previously reported for IL-2 in the same samples, and IL-1 alpha pulse parameters which are concentration independent were significantly similar to those of IL-2. Furthermore, cross-correlation analysis indicated that in 83% of our subjects (5/6) there was synchronicity of IL-1 alpha and IL-2 levels. IL-1 alpha pulse parameters were in the range reported for hormones which have well-characterized pulsatility, such as growth hormone, luteinizing hormone, follicle-stimulating hormone, cortisol, beta-endorphin, and progesterone. Based on these data we speculate that a pulsatile cytokine cascade may exist in the systemic circulation.(ABSTRACT TRUNCATED AT 250 WORDS)