AJP - Endocrinology and Metabolism, Vol 261, Issue 4 E529-E538, Copyright © 1991 by American Physiological Society
Kinetics of equilibration of radioiodide in individual mouse thyroid follicles in vivo
G. Andros and S. H. Wollman
Laboratory of Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892.
Microdensitometric measurements were made on autoradiographs of radioiodide
localized in mouse thyroids subjected to various degrees of stimulation, in
which the formation of organic radioiodide was acutely blocked. Estimates
were made of the relative concentrations of radioiodide in lumens and cells
of follicles and in the nearby blood vessels. Simple models were introduced
to interpret the data. Analysis of the ratio of radioiodide concentrations
in the lumen and cells of follicles as a function of follicles size and
time after injection indicated that smaller follicles equilibrated faster
than larger follicles, that the equilibration was faster the more active
the gland was, and that the release of radioiodide from follicles in the
less active glands must be characterized by a time-dependent exit rate
constant. Analysis of the relative concentration of luminal radioiodide as
a function of follicle size at short time intervals and in the steady state
indicated that the transport properties of the average epithelial cell were
generally independent of follicle size.
