Renin and heart rate responses to haemorrhage are age dependent in conscious lambs.
The present experiments were carried out in conscious lambs (1-2 weeks old, n = 9) and older sheep (11-12 weeks old, n = 11) to determine whether the cardiovascular and endocrine responses to 0, 10 and 20 % haemorrhage were developmentally regulated. The major novel finding of our study is that throughout the first 3 months of postnatal life, there is a similar decrease in mean arterial pressure and a similar restoration of pressure to pre-haemorrhage levels, for the same degree of blood loss, yet the mechanisms used to restore pressure appear to be age dependent as follows. In lambs, but not in older sheep, heart rate increased for 1 h after 20% haemorrhage. Activation of the renin-angiotensin system was also greater and more prolonged in lambs than in older sheep following haemorrhage, and occurred at a lesser degree of blood loss. Plasma arginine vasopressin responses to haemorrhage were, however, similar in both age groups. These data provide new information that some of the mechanisms used to restore arterial pressure following blood volume depletion appear to be age dependent.
Smith
F G
FG
Departments of Physiology and Biophysics/Medicine, University of Calgary, Calgary, Alberta, Canada T2N 4N1. fsmith@ucalgary.ca
Basati
R
R
Sener
A
A
Abu-Amarah
I
I
D000375:Aging / Q000502:physiology*; D000818:Animals; D001127:Arginine Vasopressin / Q000097:blood; D001835:Body Weight / Q000502:physiology; D004702:Endocrine Glands / Q000502:physiology; D006339:Heart Rate / Q000502:physiology*; D006439:Hemodynamics / Q000502:physiology; D006470:Hemorrhage / Q000503:physiopathology*; D012079:Renal Circulation / Q000502:physiology; D012083:Renin / Q000097:blood*; D012756:Sheep
D001127:Arginine Vasopressin; D012083:Renin