A possible mediating role of polyamines in cyclic AMP-phosphodiesterase stimulation in confluent heart cell cultures

16 THE STRUCTURE AND DYNAMICS OF BIOMEMBRANES. D. Chapman. Department of Biochemistry and Chemistry, Royal Free Hospital School of Medicine, University of London, London, England. The present view of biomembrane structure will be described. This will include the role of the lipid bilayer matrix, lipid class asymmetry The mutual modulation of lipid and protein and protein organisation. dynamics will be discussed and terms such as boundary lipid and annulus lipid will be critically examined. A comparison will be made between the effect of cholesterol on lipid movement with that of intrinsic proteins. The results of physical methods for measuring protein rotation and lateral diffusion will be studied and related to certain membrane The latest views on the skeletal network of cells and the functions. influence of this network on cell shape will be examined. (This work is supported by the Wellcome Trust).

APOSSIBLEMEDIATINGK%EOFPOLYAKCNES INCYCLICZMP-PHOSPHODIES'.FERXE s-@J IN CONFLUENT e CELI, aTLTuRES. C.Cl6, B.Tantini ard C. ROS soni Caldarera. Istitito di Chimica Biologica, Universiti di Bologna, Ita lY.

In heart cell cultures the addition of spennine, spermidine or pltreseine, at relatively law concentrations, causes the decrease of CAMP content and counteracts the effectofdifferentcAMPmediated effecters. The aimof this studywas to clarifywhether erdogencuspolyamines are involved in themechanisnleadiq to the increaseof @MP-phosphcdiesterase @DE) activity. The resAts indicate that by treating confluent heart ccl 1s with diktyryl-cA!@ or noradrenaline or isoproterenol, a rapid increase of CAMP content takes place within fewminutes. This is acccmpanied by polyanine accunulation which, in turn, is follcwed by elevation of both loward high affinity PDE activities.a-Methylornithine (a-MO), a specific inhibitcar of polyanine biosynthesis, while does not pevent c?MP accunulation, significantly reduces the stirmlatory effect of the drugs on both PDE enzymes. The involvement of polyamines in PDE stimulation is also supported by the fact that a-m prevents the increase of PDE activi ty elicited

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