Several morphological methods have been conducted in pituitary research. In this review article, molecular morphological approaches to anterior pituitary hormone production, intracellular transport and secretion are discussed. In situ hybridization (ISH) at the electron microscopic (EM) level is essential for elucidating the intracellular distribution and role of mRNA in protein synthesis. EM-ISH is considered to be an important tool for clarifying the intracellular localization of mRNA and the exact site of pituitary hormone synthesis on the rough endoplasmic reticulum. A combined ISH and immunohistochemistry (IHC) under EM (EM-ISH&IHC) has sufficient ultrastructural resolution, and provides two-dimensional images of sub-cellular localization of pituitary hormone and its mRNA in a pituitary cell. The advantages of semiconductor nanocrystals (Quantum dots, Qdots) and confocal laser scanning microscopy (CLSM) enable us to obtain three-dimensional images of subcellular localization of pituitary hormone and its mRNA. Both EM-ISH&IHC and ISH & IHC using Qdots and CLSM are useful for understanding the relationship between protein and mRNA simultaneously in two or three dimensions. Another important issue is the intracellular transport and secretion of pituitary hormone. An experimental pituitary cell line, GH3 cell, which has growth hormone (GH) linked to enhanced yellow fluorescein protein (EYFP), has been established. This stable GH3 cell secretes GH linked to EYFP upon stimulated by Ca2+ influx or Ca2+ release from storage. Such green fluorescent protein (GFP) -transfected cell line is useful for the real-time visualization of the intracellular transport and secretion of pituitary hormone. These methods from conventional immunohistochemistry and fluorescein imaging enable us to visualize consecutively the process of transcription, translation, transport, and secretion of anterior pituitary hormone.
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