ANTINATRIURETIC KIDNEY RESPONSE TO WEIGHTLESSNESS

We have tested the effects of weightlessness on renal function in one subject who flew the recent week-long Russian-German MIR'92 space miss ion. Urine flow, renal sodium excretion, and the excretion of urodilat in were measured during the first and last days of the flight. Our res ults demonstrated, in contrast to expectations, that urine flow and so dium excretion during weightlessness were actually lower than the valu es obtained during preflight measurements. These results therefore are inconsistent with the commonly held hypothesis that weightlessness in duces a diuresis and natriuresis in human subjects. It would seem that further studies are necessary to resolve this issue and to determine whether currently used ground-based models of weightlessness correctly predict physiological adaptations that occur during space flight.