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European Heart Journal 1991 12(Supplement F):135-138; doi:10.1093/eurheartj/12.suppl_F.135
Copyright © 1991 by the European Society of Cardiology.
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© 1991 The European Society of Cardiology

G protein function in the ischaemic myocardium

L. Will-Shahab, W. Rosenthal*, W. Schulze and I. Küttner

Institute of Cardiovascular Research, Division of Cellular and Molecular Cardiology Berlin-Buch
* Institute of Pharmacology, Free University Berlin Germany

Correspondence: Dr. lianc Will-Shahab, Institute of Cardiovascular Research, Division of Cellular and Molecular Cardiology, Robert Rössle Str. 10, 0-1115 Berlin, Germany

The activity of adenylyl cyclase (AC) is controlled by its interaction with receptor-regulated G proteins. The efficiency to form cyclic AMP is strongly influenced by the amount, the subspecies and function of these regulatory proteins. An impairment of AC function has been shown to occur in sarcolemmal preparations (SL) of hearts exposed to either local or global ischaemia. To examine the contribution of G protein function to this phenomenon, cholera toxin (CT)-catalysed ADP-ribosylation of G1 and pertussis toxin (PT)-catalysed ADP-ribosylation of G proteins have been investigated in SL of porcine hearts exposed to global ischaemia for 15–45min. ADP-ribosylation by CT of an approximately 45kDa polypeptide was 0·46±006 and ADP-ribosylation by PT of three 39–41 kDa polypeptides was 4·77 ± 0-·77 pmol mg–1 protein in SL of non-ischaemic myocardium. Whereas no change was observed in CT-catalyzed ribosylation after 30 min of ischaemia, there was a reduction in PT-catalyzed ADP-ribosylation to 3·7±0·35pmol mg–1 protein after 30min of ischaemia. Prolongation of ischaemia to 45min did not reduce further ADP-ribosylation capacity. Quantitative immunoblot-ting of PT-sensitive G proteins suggests that the diminution of ADP-ribosylation occurred because of a loss of a-subunits of G0, Gi–1, and Gi–2from sarcolemmal membranes.

Key Words: Myocardial ischaemia • sarcolemmal membrane • adenylyl cyclase • G proteins


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