[Dielectric analysis of the rat thyroid gland by modeling the follicle as a key structure].
To correlate the dielectric behavior of the thyroid gland with its follicle structure, I examined the admittance properties of isolated rat thyroid hemilobes over the frequency range from 100 Hz up to 500 MHz. Rats were divided into three groups: control, thyroxine (T4) administered, and goitrogen (propylthiouracil, PTU) administered. In control glands, observed dielectric dispersions with a permittivity increment (delta epsilon) of 60,000 were of the beta-type having two separate characteristic frequencies (fc1 and fc2) around 12 kHz and 3 MHz. In T4- or PTU-treated thyroid, both delta epsilon and fc1 departed from those of control, resulting in the following sequences: For delta epsilon, T4 < control < PTU, and for fc1, PTU < control < T4. These contrasting results were then correlated with morphological features involved. Histomorphometry revealed apparent differences in follicular size distribution between the three groups of tissue. Based on a model analysis using curve fitting technique, I estimated the electrical conductivity of colloid to be about 2 mS/cm, a value 6-fold smaller than that of blood plasma. Another conclusion worthy of note is that the gross dielectric behavior of the thyroid gland can be interpreted only by taking the follicular structure into account.
Kozakura
K
K
Department of Physiology, Kochi Medical School, Japan.
D000818:Animals; D017097:Electric Impedance; D004594:Electrophysiology; D066298:In Vitro Techniques; D008297:Male; D008854:Microscopy, Electron; D008953:Models, Anatomic; D051381:Rats; D017208:Rats, Wistar; D013961:Thyroid Gland / Q000502:physiology* / Q000648:ultrastructure*