Hormonal regulation of pituitary glandular kallikrein: A morphometric study

We have previously identified the lactotrophs as the Glandular Kallikrein (GK) containing cells in the rat anterior pituitary using immunocytochemistry, this localization has been independently confirmed with similar methods by other groups. The purpose of the present work was to evaluate the estrogen and dopaminergic control of the GK-containing cells using a morphometric analysis. Female (200-250 g) ovariectomized rats (n = 40) were treated with estradiol (5, 10, 50 μg/rat) in the presence or absence of haloperidol (2.5 mg/Kg). The pituitaries were fixed by perfusion with Bouin's and immunostained for prolactin (PRL) or GK. The number of cells and the intensity of the staining were determined by morphometric analysis. Little GK staining was observed in pituitaries from ovariectomized rats, whereas estradiol treatment produced a marked increase in GK staining; GK-positive lactotrophs increased from 4% in control to 75% with 5 μg of estradiol, higher doses produced little further increase. However, GK staining intensity in lactotrophs was markedly dependent upon estradiol dose increasing 4-fold between 5 μg and 50 μg. Haloperidol (2.5 mg/Kg) elicited weak GK staining in 46% of the lactotrophs in the absence of estradiol, and potentiated GK staining intensity elicited with low doses of estradiol. Estradiol also produced a dose-dependent increase in pituitary mass and % lactotrophs indicating lactotroph proliferation. Estradiol produced a dose dependent increase in pituitary wet weight, % PRL-positive cells and % GK-positive cells. Pituitary weight was correlated with % lactotrophs (r = 0.992), and % GK cells (r = 0.874), and % lactotrophs was correlated was % GK cells (r = 0.978). Haloperidol slightly increased pituitary weight, % PRL or % GK cells at all estrogen doses. The results show that estrogen induction of rat anterior pituitary GK appears likely to involve a primary action to increase GK synthesis and intracellular levels in most lactotrophs, and that the dopamine receptor blockade with haloperidol has a modulator effect.