The effect of rate of blood loss by acute hemorrhage (H) on adrenocorticotropin (ACTH) and cortisol plasma concentrations was assessed in anesthetized cats. Arterial blood was withdrawn at a rapid rate (10% blood vol/min) or at a slow rate (2%/min), and responses were compared across three volumes of H (10, 20, and 30% of blood vol). After rapid rate of H, ACTH increased in proportion to volume of H (r = 0.669, P < 0.001) with a mean elevation of 124 ± 27, 267 ± 102, and 950 ± 195 pg/ml for 10, 20, and 30% H, respectively. Slow rate of H evoked a significant increase in ACTH that was not proportional to volume of H (r = 0.314, P > 0.10), and the mean change during the post-H sampling period was 611 ± 166, 828 ± 302, and 1,070 ± 239 pg/ml for 10, 20, and 30% H, respectively. Control animals showed no change in ACTH to the repeated sampling paradigm. Rapid H evoked an immediate decrease in mean arterial pressure (MAP) with a post-H recovery of MAP inversely proportionate to volume of H (r = -0.552, P < 0.01). Slow H caused a progressive decrease in MAP with no significant post-H recovery of MAP at any volume of H. Cortisol concentration increased in proportion to volume of H after rapid H (r = 0.515, P < 0.025), but not after slow H. The data indicate that 1) rate and volume of blood loss determine the ACTH response to H, 2) recovery of MAP after rapid H may attenuate the increase in ACTH, and 3) an apparent dissociation between the ACTH and cortisol responses to slow H is seen after small volumes of H, but not after large H volumes.
|Original language||English (US)|
|Journal||American Journal of Physiology - Endocrinology and Metabolism|
|State||Published - 1986|