We examined the topographic cell affinity of different types of hormone-pro
ducing cells in the rat anterior pituitary gland. Pituitaries were removed
from 8-10 week-old male SID rats, and were fixed in sublimate-formalin. The
40 mum sections were obtained with a Microslicer, then double-immunolabele
d (FITC and TexasRed methods) using antibodies against five types of pituit
ary hormones. Topographic affinity was examined three-dimensionally using a
confocal microscope, and was expressed as attachment rate. Statistical ana
lysis revealed that the different types of hormone-producing cells did not
exist at random locations in the gland, but rather showed specific topograp
hic affinities. The following pairs of cell types were observed to have sig
nificantly high affinities: LH and PRL cells, ACTH and GH cells, and TSH an
d GH cells. In contrast, the following pairs of cell types were observed to
have no significant affinities: GH and PRL cells, ACTH and LH cells, TSH a
nd LH cells, ACTH and TSH cells, and cells of the same type. These specific
topographic affinities between different types of anterior pituitary cells
may be intimately related to cell-to-cell interactions in the gland.