Biology ETDs

Publication Date



Seven parameters were chosen to characterize131I metabolism in the Beagle, three were derived from the thyroid uptake -retention curve [maximum thyroid uptake, time to 90% maximum uptake, and biological half-life] and four from the two component whole-body131I retention curve [component intercept values, and component half-times]. These parameters were used to compare 131I metabolism in three age groups [6 , 18 , and 48 months], each consisting of six Beagles exposed to a single dose of 131I [ 100-300 µCi] by the inhalation route. An analysis of variance was performed on each parameter in this study. For six of these parameters the variability among the 18 individual dogs was larger than that among the three age groups pointing to the absence of age -related effects in 131I metabolism at a 95% confidence level. The only exception was found with the first component intercept parameter.

The same seven parameters were used in a second study to compare the metabolism of 131I in the 18-month-old Beagle exposed to a single dose of 131I [50-300 µCi] by inhalation, intravenous, and oral routes [six dogs were used in each route group]. Performing an analysis of variance on each parameter in this study showed that route-related variability in 131I metabolism was statistically smaller than that variability normally existing among the individual dogs at a 95% confidence level.

A tissue disturbing study showed major 131I accumulation of over 1% of the initial body burden in the thyroid, stomach contents, blood, and stomach. The stomach cleared over 20% of the initial 131I body burden during the first 24 hours post-exposure as compared with a 7% initial body burden clearance by the thyroid during the same interval pointing to a smaller initial clearance rate by the thyroid. Over two-thirds of the initial 131I body burden appeared in the excreta during the first 48 hours postexposure.

Artificially high percentage aerosol deposition values, which ranged up to 190%, presumably were due to low 131I aerosol concentration analyses. The formation of volatile 131I2, which was poorly retained on the collection filters, was probably the major cause of this error in these analyses.

Thyroid doses calculated for all of the dogs in this experiment ranged between 140 and 1900 rads and were considered low enough not to cause metabolic disturbances that have been reported at higher dose levels. An analysis of variance indicated that at the 95% confidence level similar thyroid radiation doses per µCi 131I administered were experienced by all dogs in this experiment regardless of age or route of exposure.

The observation that the dietary iodine intake of our dogs [700 µg per day] was twice that recommended by the NASNRC Committee [breed unspecified] suggested the possibility of lower maximal 131I thyroid uptake values in our data as compared with dogs which were maintained on lower dietary iodine level.

Document Type


Degree Name


Level of Degree


Department Name

UNM Biology Department

First Committee Member (Chair)

Martin William Fleck

Second Committee Member

Roger O. McClellan

Third Committee Member

Bruce B. Boecker

Fourth Committee Member

Marvin LeRoy Riedesel

Fifth Committee Member

Clarence Clayton Hoff

Included in

Biology Commons