Elimination rate of 65Zn as a measure of food intake: a validation study in the mouse (Mus sp.).

We measured elimination of 65Zn in white mice (Mus musculus) using daily whole body counting. Thirteen male mice were randomly divided into three groups, each maintained at a different temperature. Each animal was labeled with 65Zn on day 0 and monitored over days 0-48 postinjection. Daily food intake and body masses of all the animals were measured. We evaluated the ability of derived components of the 65Zn elimination curves to predict food intake over different phases of the measurement period. Food intake was significantly different between temperature groups; temporal variation in food intake was not intercorrelated between groups. Whole body elimination of 65Zn involved a rapid decline over days 0-1, followed by a biexponential decline in counts over days 1-48. Components of the first phase of the biexponential elimination curve were not significantly related to food intake. The rate (k2) of isotope elimination in the second phase was significantly related to mean food intake over days 25-48, 13-24, and 37-48. Rate of turnover in the second phase of elimination, incorporating the variation in zinc body pool size (k2 x 1/N2), where N2 is the constant of the second phase of elimination, was the best predictor of food intake and accounted for 60% of the variability over days 37-48.

Zinc65 absorption in patients with carcinoma of the prostate.

The intestinal absorption of 65 Zn was determined in patients with carcinoma of the prostate prior to treatment and during estrogen therapy. Following an oral tracer dose of 65 ZnCl2, plasma levels and urinary and fecal excretions of 65 Zn were determined. The absorption of 65 Zn was low in six of eight patients, particularly in three patients who had extensive metastatic bone involvement. During estrogen therapy the absorption of 65 Zn increased markedly in these patients, and this increase correlated with the clinical remission of the neoplastic process. In one patient who did not respond to estrogen therapy, 65 Zn absorption was normal prior to treatment and did not increase during estrogen therapy. In patients free of neoplasia estrogen administration did not increase 65 Zn absorption, and even decreased it. These results indicate that the intestinal absorption of 65 Zn is decreased during the active phase of carcinoma of the prostate and improves during clinical remission induced by estrogen therapy.