Determination of the Cell Number of Each Cell Type in the Anterior Pituitary of Euthyroid and Hypothyroid Rats1

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Abstract
A method combining enzymatic cellular dispersal, direct cell counting, differential cell counts at the EM level and DNA determinations was devised and employed for determination of cell numbers of each anterior pituitary cell type in euthyroid (E) and hypothyroid (Tx) rats. Pituitaries from Tx [thyroidectomized] rats increased cell number as demonstrated by a mean 33.7% increase in DNA content (.mu.g DNA/pituitary). Total cells increased from (3.14 .+-. 0.36) .times. 106 in E rats to (3.98 .+-. 0.27) .times. 106 in Tx rats, P < 0.005. Cellular DNA content (pg/cell) in E rats, 10.84 .times. 0.63 (SD), was indistinguishable statistically from that of Tx rats, 11.24 .+-. 0.52. Cell distribution among various pituitary cell types was virtually identical when determined in pellets from dispersed cells and randomized solid tissue from the same groups of E and Tx rats. Apparently there was no selective cell loss during the cell dispersion procedure. Major changes in Tx rats compared to E rats were a marked increase in percentage of thyrotrophs, from 10.7 .+-. 1.75 (E) to 34.4 .+-. 1.0 (Tx), and a decrease in percentage of somatotrophs, from 55.3 .+-. 1.82 to 15.3 .+-. 0.97. Calculated cell distribution showed that the number of thyrotrophs decreased from 1.74 .+-. 0.11 to 0.61 .+-. 0.02 millions in hypothyroid rats. This method provides a quantitative estimate of changes in pituitary cell populations in different hormonal states and should be useful in studies of kinetics of pituitary cell replication and removal.