Beta-endorphin secretion at the time of sudden death due to cardiac or respiratory failure

Using male and female Wistar rats, pituitary response to cardiac and respiratory failure type (CFT and RFT) sudden death caused by the intravenous administration of KC1 and SCC, respectively, was examined by analyzing variation in pituitary immunoreactive beta-endorphin (IR-beta-EP) levels determined by radioimmunoassay after death and in circulating IR-beta-EP levels during periods of agony. In the pituitary gland of both sexes which differed significantly in ratio of the organ weight to body weight for CFT and RFT (CFT greater than RFT), IR-beta-EP was significantly less in RFT than in CFT (p less than 0.05). No variation in plasma IR-beta-EP was noted during short periods of agony in CFT, but it markedly increased during long periods of agony in RFT. The highest elevation at 2 or 4 minutes after SCC administration was about 3 times the preadministration value for IR-beta-EP in males (p less than 0.01). But elevation in females was lower than in males. Rise plasma IR-beta-EP during agony of RFT is regarded to be of pituitary origin due to dexamethasone treatment. The pituitary was thus concluded to respond more to the fatal agony in RFT than in CFT.