Abstract 329

Introduction

The chick embryo develops a protective response to acute hypoxia during the second half of incubation. One part of this response is a redistribution of the cardiac output in favor of heart and brain. This redistribution seems to be the result of activation of the autonomous nerve system by chemoreceptor response and by circulating catecholamines. In the present study we measured plasma catecholamine concentrations in normoxia and after 5 minutes of hypoxia (100%N2)in chick embryos at day 10, 13, 16 and 19 of incubation. The normal incubation time until hatching is 21 days.

Methods

Fertilized eggs were placed in a Plexi Glass box in which oxygen concentration could be changed. The eggs were opened at the air cell. The chorioallantoic membrane was carefully opened without damaging the vessels in the membrane. The chorioallantoic artery was visualized and gently lifted to the surface. After 5 minutes of either normoxia or anoxia the artery was punctured and a blood sample withdrawn. Catecholamines were measured using HPLC.

Results: Mean catecholamine concentrations during normoxia (21% O2) and hypoxia (0% O2) in ng/ml (Table)

Table 1 No caption available
Full size table

Conclusion

Catecholamine levels rise in response to hypoxia from day 13 and this rise seems to increase with incubation time. Catecholamines play a role in the redistribution of the cardiac output.