Smith F G, McWeeny O J, Robillard J E
Department of Medical Physiology, University of Calgary, Alberta, Canada.
Am J Physiol. 1996 May;270(5 Pt 2):H1718-25. doi: 10.1152/ajpheart.1996.270.5.H1718.
To further investigate the maturation of the cardiopulmonary baroreflex, we measured the effects of a 45-min blood volume expansion to an increase in right atrial pressure of approximately 4 mmHg in chronically instrumented newborn (n = 17) and older lambs (n = 14). Measurements included various parameters of endocrine, cardiovascular, and renal function and concomitant recording of renal sympathetic nerve activity (RSNA). During blood volume expansion, RSNA was inhibited to a similar extent in newborns and older lambs when atrial pressures were increased by approximately 4 mmHg. A sympathoinhibition persisted in newborns but was only transient in older lambs. In newborn lambs, heart rate decreased in response to blood volume expansion, whereas heart rate remained constant after blood volume expansion in older lambs. The renal and endocrine responses to blood volume expansion were, however, similar in newborns and older lambs. These data provide evidence that when atrial pressures are matched, the renal and endocrine responses to blood volume expansion are similar, but there are differential cardiovascular and RSNA responses. Any reduced ability of the newborn kidney to excrete a volume load is therefore probably related to maturational differences in its distribution between the capacitance vessels and the heart.
为了进一步研究心肺压力反射的成熟情况，我们测量了在长期植入仪器的新生羔羊（n = 17）和较大羔羊（n = 14）中，45分钟血容量扩张使右心房压力增加约4 mmHg的影响。测量包括内分泌、心血管和肾功能的各种参数，并同时记录肾交感神经活动（RSNA）。在血容量扩张期间，当心房压力增加约4 mmHg时，新生羔羊和较大羔羊的RSNA受到类似程度的抑制。新生羔羊中交感神经抑制持续存在，而在较大羔羊中只是短暂的。在新生羔羊中，心率随血容量扩张而降低，而在较大羔羊中血容量扩张后心率保持恒定。然而，新生羔羊和较大羔羊对血容量扩张的肾脏和内分泌反应相似。这些数据表明，当心房压力相匹配时，对血容量扩张的肾脏和内分泌反应相似，但心血管和RSNA反应存在差异。因此，新生肾脏排泄容量负荷能力的任何降低可能与其在容量血管和心脏之间分布的成熟差异有关。
