Adenosine causes camp-dependent coordinate activation of chick embryo red cell carbonic anhydrase and 2,3dpg synthesis. Glombitza, Stefan, Stefanie Dragon, Margit Berghammer, Markus Pannermayr, Rosemarie Baumann. Physiologisches Institut, Universit[umlaut]at Regensburg, 93047 Regensburg, Germany
APStracts 3:0160R, 1996.
In late chick embryos coordinate activation of red cell carbonic anhydrase?II (CAII) and 2,3-bisphosphoglycerate (2,3DPG) synthesis is initiated by hypoxia. The effects are mediated by unidentified hormonal effectors resident in chick plasma. In the present investigation we have analyzed the effect of adenosine receptor stimulation on embryonic red cell CAII and 2,3DPG synthesis. We find that primitive and definitive embryonic red cells from chick have an A2a-adenosine receptor. Stimulation of the receptor with metabolically stable adenosine analogues causes a large increase of red cell cAMP and subsequent activation of red cell CAII and 2,3DPG production in definitive red cells and of CAII synthesis in primitive red cells. Direct stimulation of adenylyl cyclase with forskolin has the same effect. Analysis of red cell protein pattern after labelling with 35S-methionine shows that stimulation of red cell cAMP levels activates synthesis of several other proteins aside from CAII. Presence of actinomycin?D inhibits cAMP-dependent changes of protein synthesis, indicating that cAMP-dependent transcriptional activation is required. In contrast to the stable adenosine receptor analogues adenosine itself was a very weak agonist, unless its metabolism was significantly inhibited. Thus besides adenosine other effectors of the adenylyl cyclase system are likely to be involved in the oxygen pressure dependent regulation of red cell metabolism in late development of avian embryos. 

Received 12 May 1995; accepted in final form 2 April 1996.
APS Manuscript Number R282-5.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 8 May 96