3-DIMENSIONAL ANALYSIS OF THE DEVELOPING PITUITARY-GLAND IN THE MOUSE

Prenatal development of the mouse pituitary gland was analyzed in thre e-dimensions by using confocal laser-scanning microscopy. In any whole mount preparation of the fetal pituitary gland from day 10 to day 18, immunofluorescence of laminin was observed in the deeper regions of th e organ and demarcated the boundary of the epithelial tissue from the surrounding mesenchyme, Three-dimensional capillary networks in the fe tal pituitary gland at day 13, day 15, and day 18 were visualized clea rly by perfusing the blood vessels with an fluorescein isothiocyanate- labelled gelatin solution. During days 12-14, cellular plates protrude d from the anterior wall of the pituitary anlage and extended toward t he base of the infundibulum. At the same time, the mesenchyme situated among the cellular plates separated from the surrounding mesenchyme e xcept at the anteroventral portion of the anlage, In a posterior wall of the anlage, intercellular depositions of laminin were found among t he epithelial cells, some of which reached the laminin sheet in the ba sement membrane of the anlage, From days 15-18, the pituitary gland en larged, and the mesenchyme spread radially from the median anteroventr al portion to the lateral, posterior, and dorsal regions and finally e xpanded throughout the entire organ. At the periphery, the mesenchyme in the pituitary gland connected with that surrounding the capsule. La minin was still found in the intercellular spaces between the epitheli al cells, and most of the intercellular depositions of laminin were co mbined with the laminin sheet in the epithelial basement membrane. An abundance of vessels entered the organ from its anteroventral portion, spread, and connected with one another throughout the gland, similar to the distribution of mesenchyme. Intercellular laminin would induce the polarization of the contacting epithelial cells, resulting in rear rangement of the epithelial cells. The mesenchyme might spread in the pituitary gland, providing the intercellular laminin a foothold, in or der to cleave the epithelial cell mass into lobules, The development o f capillary nets in the adenohypophysis corresponded well with that of the mesenchyme. Because laminin localizes mainly in the basement memb rane in the fetal organs, immunostaining of laminin clearly indicates the boundary between epithelial tissue and the mesenchyme, Three-dimen sional observation of laminin in wholemount preparation is very useful for studying morphogenesis. (C) 1998 Wiley-Liss, Inc.