STUDIES IN HISTOCHEMISTRY: LXXXII. DETERMINATION OF VITAMIN A IN MICROGRAM SAMPLES OF TISSUE AND ITS QUANTITATIVE HISTOLOGICAL DISTRIBUTION IN THE RAT ADRENAL

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Abstract
A fluorometric procedure is presented for the determinations of vitamin A in small tissue samples, e. g., microtome sections, to enable correlation of analytical data with histology. Measurements may be made over the range, 3 x 10–12–6 x 10–10 moles of the vitamin (0.86-17 mµg of vitamin A alcohol), the quantities per 60 µl of solution used in the microcuvettes for fluorometry. Optimal conditions for certain of the analytical steps and for extraction of the vitamin from tissue were studied. Quantitative recoveries of vitamin added to tissue were obtained, and the reproducibility of the analysis of tissue was observed to have a standard deviation of 4%. In preliminary experiments, a mean vitamin A per rat adrenal was found to be 2.3 mµmoles, and the mean concentration 317 mµmoles/g, dry weight. A study of the quantitative histological distribution of the vitamin in the adrenal revealed greatest concentrations (4.7 x 10–12 moles/µg of proten-nitrogen) in the region where the glomerulosa and fasciculata join, and the concentration fell steadily through the fasciculata and reticularis to a low (0.9 x 10–12 moles/µg of protein-nitrogen) in the medulla.

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