Clearance of 125I-labeled interleukin-6 from brain into blood following intracerebroventricular injection in rats

Endocrinology. 1997 Nov;138(11):4830-6. doi: 10.1210/endo.138.11.5533.


To test the hypothesis that interleukin-6 (IL-6) induced within the brain can be released into peripheral blood, 125I-labeled IL-6 was injected into the lateral cerebral ventricle of rats, and its concentration in peripheral blood followed serially. Acid-precipitable tracer appeared within 5 min of injection and entered the blood following first-order kinetics (fractional rate, 0.0116 +/- 0.0022/min). Comparison of areas under the curve of intracerebroventricular (icv) vs. iv injection showed that 37.1-46.5% of tracer injected into the lateral cerebral ventricle appeared in the blood over a 4-h period. icv IL-6 exits at least in part via venous drainage (superior sagittal sinus/aortic concentration gradient was 1.47 +/- 0.23 and 3.05 +/- 0.87 in two separate groups). Prior icv injection of human IL-1beta (100 ng) did not alter rate of degradation or of exit ofradioiodine-labeled IL-6 from the brain. These studies indicate that a relatively high proportion of IL-6 that arises in the brain enters the peripheral circulation. Direct secretion of IL-6 from brain to blood may be a mechanism by which the brain modifies peripheral metabolic, endocrine, and immune activity.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Aorta
  • Brain / metabolism*
  • Cranial Sinuses
  • Injections, Intraventricular
  • Interleukin-1 / pharmacology
  • Interleukin-6 / blood*
  • Interleukin-6 / cerebrospinal fluid
  • Interleukin-6 / pharmacokinetics*
  • Iodine Radioisotopes
  • Male
  • Osmolar Concentration
  • Rats
  • Rats, Sprague-Dawley


  • Interleukin-1
  • Interleukin-6
  • Iodine Radioisotopes