Miki K, Shiraki K, Sagawa S, de Bold A J, Hong S K
Department of Physiology, School of Medicine, University of Occupational and Environmental Health, Kitakyushu, Japan.
Am J Physiol. 1988 Feb;254(2 Pt 2):R235-41. doi: 10.1152/ajpregu.1988.254.2.R235.
The present investigation was undertaken to test the hypothesis that a circadian variation in the atrial natriuretic factor (ANF) response is responsible for the nocturnal inhibition of renal responses to head-out immersion (HOI). Plasma ANF responses to a 3-h HOI (water temperature 34.5 +/- 0.5 degrees C) were studied during day (1000-1300) and night (2400-0300) in six hydropenic male human subjects. In agreement with the previous observations, the renal responses, especially the diuresis, to HOI were attenuated at night compared with the day; furthermore, plasma renin activity decreased to the same low level during HOI at both day and night. Plasma ANF during time control periods was 30-40 pg/ml without showing any circadian variation. Moreover, plasma ANF showed a similar twofold increase within 1 h of HOI and was maintained at this elevated level throughout the 3-h HOI period in both the daytime and the nighttime series. On termination of HOI, plasma ANF decreased linearly to the pre-HOI level within 1 h. Hematocrit during time control periods was higher during the day compared with the night (P less than 0.05). Although HOI appears to induce a transient increase in plasma volume (as indicated by decreases in hematocrit) during the 1 h of HOI, the magnitude of the decrease in the latter parameters was not different between day and night. It is concluded that nocturnal inhibition of renal responses to HOI cannot be fully accounted for by circadian differences in the ANF and fluid shift response to HOI.
心房利钠因子（ANF）反应的昼夜变化是导致夜间头部浸入水中（HOI）时肾脏反应受抑制的原因。在6名禁水男性受试者中，研究了白天（1000 - 1300）和夜间（2400 - 0300）血浆ANF对3小时HOI（水温34.5±0.5摄氏度）的反应。与先前的观察结果一致，与白天相比，夜间HOI时肾脏反应，尤其是利尿作用减弱；此外，白天和夜间HOI期间血浆肾素活性均降至相同的低水平。时间控制期的血浆ANF为30 - 40 pg/ml，未显示出任何昼夜变化。此外，无论是白天还是夜间系列，血浆ANF在HOI后1小时内均有类似的两倍增加，并在整个3小时HOI期间维持在这一升高水平。HOI结束时，血浆ANF在1小时内线性下降至HOI前水平。时间控制期的血细胞比容白天高于夜间（P<0.05）。虽然HOI似乎在HOI的1小时内导致血浆容量短暂增加（以血细胞比容降低为指标），但这些参数下降的幅度在白天和夜间并无差异。结论是，夜间肾脏对HOI反应的抑制不能完全由ANF的昼夜差异和HOI引起的液体转移反应来解释。
