Noradrenaline as mediator of hypoxic stimulation of avian embryonic red cell carbonic anhydrase and 2,3dpg synthesis. Dragon, Stefanie, Stefan Glombitza, Robert G[diaeresis]otz, and Rosemarie Baumann. Physiologisches Institut Universit[umlaut]at Regensburg
APStracts 3:0159R, 1996.
Hypoxia is the stimulus for activation of red cell carbonic anhydrase II (CAII) and 2,3- bisphosphoglycerate (2,3DPG) synthesis of chick red cells during late embryonic development. We have tested if plasma catecholamines are involved as hormonal mediators, as hypoxia is a well-known stimulus for catecholamine release in mammalian fetuses. Plasma catecholamines were measured in 8 to 16 day (d) old chick embryos. Plasma levels of noradrenaline (NA) were initially low, but its concentration increased rapidly from 2.7?nM (d?12) to 13.4?nM (d?13) and 25.5?nM at d?16. Adrenaline (AD) was not detectable before d?13.- Short term hypoxic exposure of d?11 embryos (1?h incubation at 13.5%?O2) increased plasma NA concentration fivefold compared to the controls but had no effect on AD. - During 15?h in vitro incubation of red cells from d?11, addition of 1?[mu]M NA to the incubation medium increased the red cell 2.3DPG concentration nearly threefold and CAII activity sixfold compared to the control. The CAII-activity and 2,3DPG-concentration were also increased when cells were incubated with plasma from late chick embryos. The activation was induced by [beta]-adrenergic stimulation of adenylyl cyclase. Atenolol and propranolol blocked the effects of NA and embryonic chick plasma. Analysis of de?novo protein synthesis (35S-methionine incorporation) demonstrated that catecholamines stimulate the synthesis of several proteins besides CAII. The results indicate that developmental changes of plasma NA concentration are instrumental in the cAMP-dependent activation of CAII and 2.3DPG synthesis of red cells from late chick embryos 

Received 12 May 1995; accepted in final form 2 April 1996.
APS Manuscript Number R283-5.
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