Biological Effects of Blood Loss: Implications for Sampling Volumes and Techniques * Commentary: H. Richard Adams

Corticosterone, prolactin, and growth hormone responses to 5 s of handling or 3 min of novel environment were compared in rats at crest and trough of the diurnal adrenal rhythm 0, 5, 15, 30, and 60 min after stimulation. All hormones responded to stimulation, corticosterone and prolactin with a dramatic rise, and growth hormone with a precipitous fall. Resting corticosterone levels evidenced the expected diurnal variation, and prolactin but not growth hormone also showed a baseline diurnal variation of small magnitude at the times studied. Growth hormone response characteristics were unaffected by time of day or type of stimulation. Both corticosterone and prolactin response profiles differed at both times of day and following both types of stimulation. Corticosterone and prolactin levels were highly correlated and each was negatively correlated with growth hormone levels. This study confirms that hormone responses to stress are complex and depend not only on the stimulus but the context of stimulation.

The effects of hemorrhage on arterial pressure, blood flows, and resistances in the coronary, mesenteric, renal, and iliac beds of healthy, conscious dogs and intact, tranquilized baboons were studied. Mild nonhypotensive hemorrhage (14+/-2 ml/kg) increased heart rate and mesenteric and iliac resistances slightly but significantly, and decreased renal resistance (-13+/-2%). Moderate hypotensive hemorrhage, 26+/-2 ml/kg, reduced mean arterial pressure (-23+/-2 mm Hg) and blood flows to the mesenteric (-56+/-3%), iliac (-58+/-5%), and coronary (-39+/-4%) vascular beds, and increased heart rate (+89+/-9 beats/min) and resistances in the mesenteric (+73+/-15%), iliac (+102+/-19%), and coronary (+27+/-5%) beds. In contrast to the other beds, renal flow rose 11+/-6% above control and renal resistance fell 31+/-2% below control. Renal vasodilatation with hemorrhage was also observed in five baboons. The increases in mesenteric and iliac resistances were blocked almost completely by phentolamine, while the increase in coronary resistance was only partially blocked by phentolamine. The renal dilatation was not blocked by phentolamine, propranolol, atropine, or tripelennamine, but was prevented by indomethacin, suggesting that this dilatation was mediated by a prostaglandin-like compound. Thus the peripheral vascular responses to hemorrhage involve intense vasoconstriction in the mesenteric and iliac beds. In the normal conscious dog and the intact, tranquilized primate, the renal bed does not share in the augmentation of total peripheral resistance with nonhypotensive and moderate hypotensive hemorrhage, but does with more severe hemorrhage. In fact, renal vasodilatation occurs with nonhypotensive or moderate hypotensive hemorrhage, which can be prevented by blockade of prostaglandin synthetase with indomethacin.