Three cytologically distinct cell populations were identified, in addition to ciliated cells, when a unit gravity sedimentation procedure was applied to pronase-dispersed rabbit endocervical cells. Two of these cell populations contained histochemically distinguishable (periodic acid- Schiff [PAS]) mucoproteins and were designated vacuolated and granular PAS-positive cells. The third, designated as vacuolated PAS-negative, did not contain secretory granules. Cell integrity was confirmed by trypan blue dye exclusion, [(3)H]leucine incorporation, and ultrastructural analysis. To demonstrate hormonal modulation of endocervical cell morphology, cell distribution profiles were compared from animals in different hormonal states. In the absence of estrogen dominance, PAS- positive cells from 5-d pseudopregnant rabbits were reduced 50 percent, while vacuolated PAS-negative cells increased fourfold as compared with estrous cell populations. The PAS-positive cells sedimented toward the top of the gradient where the bovine serum albumin concentrations were lower, consistent with a reduction in the number of secretory granules. In the sustained absence of ovarian steroid hormones, the number of PAS-positive mucous cells from ovariectomized rabbits was reduced to only 4 percent of the total endocervical cell population.
The biosynthetic capacity of isolated endocervical cells was determined by incubating the three nonciliated cell populations from estrous and 5-d pseudopregnant rabbits for 36 h with the mucin precursor, [(14)C]N-acetyl- D-glucosamine. Only PAS-positive cells incorporated significant amounts of labeled precursor. This study indicates that steroid hormones influence cervical secretions by modulating the type of endocervical cells.