Specific Receptors for Inositol 1,4,5-Trisphosphate in Endocrine Target Tissues
The hydrolysis of inositol lipids by phospholipase C is believed to be the primary mechanism by which many hormones elicit calcium-mediated metabolic and secretory responses in their respective target tissues. The initiating event in this signaling system is the phosphodiesteratic cleavage of phosphatidylinositol-4,5-bisphosphate to generate the inositol-1,4,5-trisphosphate (IP3), which can mobilize intracellular Ca2+(Berridge and Irvine, 1984), and 1,2 diacylglycerol, which stimulates protein kinase C (Nishizuka, 1984). IP3has been shown to release Ca2+ from nonmitochondrial stores in a wide variety of cells (Strebet al., 1983; Josephet al., 1984; for review see Abdel-Latif, 1986). The mechanism of IP3-induced Ca2+ release is not yet known but it has been postulated that IP3interacts with a specific receptor on the endoplasmic reticulum. The purpose of this chapter is to describe the properties of specific binding sites for IP3in subcellular preparations of the adrenal cortex, the anterior pituitary gland, and the liver. The physiological relevance of these putative receptors is assessed by the study of Ca2+ -releasing activity of IP3in the same tissue preparations.
KeywordsPhytic Acid Adrenal Cortex Anterior Pituitary Gland Liver Plasma Membrane Plasma Membrane Fraction
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