Structural and functional differences between prolactin cells from the inner and outer zones of the male rat anterior pituitary

Abstract

The aim of this study was to compare the ultrastructure of prolactin cells in the inner and outer zones of the male rat anterior pituitary, and to relate their morphological features to their secretory activity, by means of standard and ultrastructural reverse hemolytic plaque assays (RHPA). The immuno-ultrastructural study showed that in the inner pituitary small-granulated cells represented 52% of the prolactin cells, there being only 5% with large granules, whereas the prolactin cells with large granules accounted for 52% in the outer zone, with only 7% being small-granulated. Percentages of cells with intermediate-sized granules were 43% and 41%, respectively. Analysis of RHPA data revealed that, under basal conditions, prolactin cells secreted more actively in the inner zone than in the outer zone. Stimulation with thyrotropin-releasing hormone or KCl treatment increased the percentage of secretors and the sizes of hemolytic plaques in both zones. However, in response to thyrotropin-releasing hormone, the increase in number of secretors was always higher in the outer zone, whereas the enlargement of plaque sizes was greater for the "inner" cells. These findings are in favor of the small-granulated cells, which predominate in the inner zone, being in a stage of active secretion and responsiveness.

Identification of Endocrine Cell Populations Expressing the AT1BSubtype of Angiotensin II Receptors in the Anterior Pituitary

“…Indeed, in PRL cells, the existence of both morphological and functional heterogeneities is known (23,24). Indeed, in PRL cells, the existence of both morphological and functional heterogeneities is known (23,24).…”

Differential routing of coexisting neuropeptides in vasopressin neurons

“…The best results were obtained from Vibratome sections, embedded at −30 °C in hydrophilic Lowicryl ® K4M resin (Sigma) by the progressive lowering of temperature technique using a Reichert AFS system (Leica, Wien, Austria) according to the instruction manual. Ultrathin sections from Lowicryl blocks were mounted on gold grids and submitted to the postembedding immunogold procedure for the detection of vasopressin and galanin as previously described (Ozawa et al ., 1994; Vila‐Porcile & Barret, 1996). Briefly, the grids were successively floated on drops of 50 m m ammonium chloride in Tris‐buffered saline (TBS) for 15 min and of TBS supplemented with 1% bovine serum albumin (TBS‐BSA) for 1 h. Grids were then incubated overnight at 4 °C on drops of the primary antibodies diluted in TBS‐BSA.…”

Angiotensinogen, Prorenin, and Renin Are Co-localized in the Secretory Granules of All Glandular Cells of the Rat Anterior Pituitary: An Immunoultrastructural Study

“…The detection of RAS components (AGT, prorenin, and renin) required longer incubation, from 4 to 5 hr at room temperature (RT) or 15 to 20 hr at 4C, compared to 1-2 hr at RT for hormone detection. Grids were treated on drops of different reagents, as previously described (Ozawa et al 1994;Vila-Porcile and Barret 1996), using specific antibodies diluted in Tris-maleate buffer supplemented with 1% BSA and related colloidal gold conjugates in the same buffer (1-2 hr). Grids were air-dried, stained for 8-10 sec with 2% uranyl acetate in 50% ethanol, and examined under a LEO 906 electron microscope (Oberkochen, Germany).…”