Determination of the cell number of each cell type in the anterior pituitary of euthyroid and hypothyroid rats.

A method combining enzymatic cellular dispersal, direct cell counting, differential cell counts at the electron microscope level and DNA determinations was devised and employed for determination of the cell numbers of each anterior pituitary cell type in euthyroid (E) and hypothyroid Tx) rats. Pituitaries from Tx rats had increased cell number as demonstrated by a mean 33.7% increase in DNA content (microgram DNA/pituitary). Total cells increased from (3.14 +/- 0.36) X 10(6) in E rats to (3.98 +/- 0.27) X 10(6) in Tx rats. P less than 0.005. The cellular DNA content (g/cell) in E rats ,10.84 +/- 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. These data indicated that 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. The calculated cell distribution showed that the number of thyrotrophs increased from 0.34 +/- 0.02 to 1.37 +/- 0.05 millions per pituitary and somatotrophs decreased from 1.74 +/- 0.11 to 0.61 +/- 0.02 millions in hypothyroid rats. The method described herein thus provides a quantitative estimate of changes in pituitary cell populations in different hormonal states and should be useful in studies of the kinetics of pituitary cell replication and removal.