title: Adrenal medullary responses to repeated hemorrhage in the anesthetized dog.
abstract: Adrenal secretory rates of catecholamines in response to a repeated stimulus have not been described. We have used repeated small hemorrhages spaced 24 h apart in pentobarbital anesthetized dogs prepared with a chronic adrenal venous catheter to study this question. Our results confirm earlier reports that an initial 7.5 ml/kg hemorrhage is a mild stimulus to the adrenal medullar secretion of epinephrine and norepinephrine, However, when this stimulus is repeated 24 h later, a greatly potentiated secretory response of both hormones is seen. Cardiovascular changes after hemorrhage did not differ on the 2 days. Repeated 3.75 ml/kg hemorrhages did not lead to augmented adrenal medullary secretion of catecholamines on day 2. These data indicate that there is a factor associated with hemorrhage that potentiates the adrenal medullary response to second small hemorrhage. This factor appears to be subject to a threshold that lies between a 3.75 and 7.5 ml/kg hemorrhage. A significant catecholamine response on day 1 was not essential for the potentiated response on day 2. Thus, this phenomenon does not appear to be the result of adrenal enzyme induction as a consequence of prior adrenal medullary stimulation.
mesh_terms: D000307:Adrenal Gland Diseases / Q000503:physiopathology; D000313:Adrenal Medulla / Q000503:physiopathology*; D000818:Animals; D001794:Blood Pressure; D004285:Dogs; D004837:Epinephrine / Q000378:metabolism; D005260:Female; D006339:Heart Rate; D006470:Hemorrhage / Q000503:physiopathology*; D008297:Male; D009638:Norepinephrine / Q000378:metabolism; D013997:Time Factors
chemical_list: D009638:Norepinephrine; D004837:Epinephrine