Role of extracellular calcium in the action of vasopressin on hepatic glycogenolysis

Calcium antagonizes the magnesium‐induced high affinity state of the hepatic vasopressin receptor for the agonist interaction

“…A general conclusion emerging from these investigations supports the presence of a homogeneous population of V1 receptors in rat liver. Further, we (Gopalakrishnan et al, 1988) documented a marked increase in the agonist binding affinity induced by Mg2+ (1 mM) such that the estimated KD values (-100pM) for [3H]-AVP were in the range that agreed well with the reported half-maximal concentrations of AVP in promoting hepatic glycogenolysis (Keppens & De Wulf, 1975;Stubbs et al, 1976;Cantau et al, 1980;Mauger et al, 1984). In addition, we also demonstrated a decrease in the antagonist binding affinity caused by Mg2".…”

“…The vasoconstrictor and the antidiuretic actions of arginine vasopressin (AVP) are mediated by the activation of V1 and V2 receptors, respectively (Michell et al, 1979). Recent evidence also supports the view that AVP enhances hepatic glycogenolysis by the activation of vascular type V1 receptors located on liver plasma membranes (Stubbs et al, 1976;Michell et al, 1979;Cantau et al, 1980). Several studies including recent work from our laboratory have characterized in vitro the hepatic V1 receptor in rat liver membrane and intact hepatocytes (Cantau et al, 1980;Fahrenholz et al, 1985;Fishman et al, 1985;Gopalakrishnan et al, 1986;1988;Cornett & Cate, 1989).…”

Reduced preabsorptive insulin response in aged rats: differential effects of amphetamine and arginine-vasopressin

“…The preabsorptive insulin response was also potentiated by the neuropeptide AVP in young, but not in aged rats. Although AVP may directly affect hepatic glucose release [27], the absence of differences in the blood glucose levels before food presentation suggests that other mechanisms are involved. There is disagreement 127 about the direct effect of AVP on B cells.…”

The Role of Futile Cycles in the Regulation of Carbohydrate Metabolism in the Liver

“…F'henylephrine and vasopressin have almost no effect on cyclic AMP nor on protein kinase activity (Sherline et al, 1972;Tolbert et al, 1973;Kirk and Hems, 1974;Keppens and De Wulf, 1975;Hutson et al, 1976;Cherrington et al, 1976;Kemp and Clark, 1978;Chan and Exton, 1978). The same agonists also stimulate glycogen breakdown (for a review, see Hems, 1977), and their effect is currently believed to be independent of cyclic AMP and mediated by ionic changes, presumably an increase in cytosolic Ca2' (Stubbs et al, 1976;Assimacopoulos-Jeannet et al, 1977;Keppens et al, 1977;van de Werve et al, 1977;Blackmore et al, 1978;Chen et al, 1978); part of this Caz+ might originate from mitochondria (Blackmore et al, 1979).…”