MODULATION OF ARGININE VASOTOCIN SECRETION IN CHICKS BY DEHYDRATION DURING EMBRYOGENESIS

The influence of low humidity during incubation (LHI) on arginine vaso tocin (AVT) secretion in male and female White Leghorn chicken embryos and chicks was investigated. LHI embryos were incubated from day 8 (E 8) to E18 at a relative humidity of 32-35%, while control embryos were incubated at 58-62%. In the control groups, plasma AVT gradually incr eased from E15 to E18, increased sharply during hatching and returned to the E18 level within 4 h. LHI did not alter the level of AVT until E18. LHI E19 males had concentrations of AVT twice as high as those of control males (39 +/- 3.9 vs 15 +/- 1.6 pmol/l, P<0.001), Augmentatio n persisted during hatching and 4 h afterwards. In LHI females additio nal elevation reached significant levels only at 4 h after hatching (5 8 +/- 13 vs 16 +/- 1.7 pmol/l, P<0.01), Deprivation of water caused an increase in plasma sodium concentrations in the 2-day-old chicks of t he control groups, while no significant changes were observed in the L HI group. Deprivation of water together with a high environmental temp erature caused an additional increase in AVT only in the LHI groups (4 2 +/- 5.2 vs 22 +/- 3.9 pmol/l, P<0.01 for males; 32 +/- 3.4 vs 19 +/- 2.8 pmol/l, P<0.01 for females). The results clearly showed that LHI leads to a more pronounced response of the AVT system on subsequent os motic and non-osmotic challenges, especially in males. Embryonal activ ation of the AVT system probably helps the organism to cope with hatch ing and posthatching stresses.