Macromolecular binding of [5,6-3H] Prostaglandin E1 in liver cytosol in vitro

Demonstration of steroid specific hormone receptors by chromatography

“…wt of 120 000 and another, more abundant, of 60-70 000 daltons. These molecular sizes are comparable to those of corticosterone [4][5][6], the 'G' [2] or the steroid II [3] receptors, although neither peak corresponds to serum transcortin (62-63 000 daltons). The close similarity in molecular sizes, and the fact that transcortin is present to variable extent in most tissue preparations, obviate the importance of filtration through Sephadex gels; these are also true of sucrose density gradients further unsuitable due to huge dissociation during the lengthy centrifugation period [4][5][6]11 ].…”

“…Some radioactivity consistently came off at 0.18 M KC1 and may consist of receptors, ligandin [3], metabolite binders [3], or the A protein [2]. In fact, a number of so-called binders [3] may indeed be explained as polymorphs of a basic unit generated as a function of exposure to high salt buffers. Passage through Sephadex G-200 columns equilibrated at physiological ionic strength and pH (7.4) revealed the presence of two components ( fig.4).…”

“…The chromatography on Sephadex-DEAE-A-50 was performed after modification of other procedures [3]. Further details are given in the text and the legends.…”

“…Although studies with displaceable binding indicate the presence of steroid-specific hormone receptors, earlier efforts [2,3] at physicochemical characterization of these intracellular binders has largely been frustrating and ambiguous, due largely to technical difficulties. As early as 1970, when this field was still accepted with scepticism, we had established techniques for chromatographic identification of steroid-binding proteins and accomplished 300-fold purification of rat liver corticosterone receptors [4][5][6][7], and recently extended them to revealing renal mineralocorticoid specific 'MR' receptors [8,9].…”

Further studies on the mechanism of phosphorylase activation in rabbit liver in response to splanchnic nerve stimulation

“…Prostaglandins may act intracellularly or at the cell membrane. There is evidence to suggest that receptors for prostaglandins exist in the plasma membrane (Smigel & Fleischer, 1974), the mitochondrial membrane (Carafoli & Crovetti, 1973) and the cytosol (Litwack, Filler, Rosenfield & Lichtash, 1973) of rat liver. Moreover, it has been postulated that some of the physiological actions of prostaglandins are linked to the movement of Ca2+ across biological membranes (Horton, 1969) and several investigators have proposed that prostaglandins can function as calcium ionophores (Kirtland & Baum, 1972;Carsten & Miller, 1977;Ohnishi & Devlin, 1979).…”