Urinary albumin in space missions

Proteinuria has been hypothesized for space missions, but research data have been lacking. Urinary albumin, as an index of proteinuria, was analyzed in frozen urine samples collected by astronauts during space missions onboard the MIR station and on ground (control). Urinary albumin was measured by a double antibody radioimmunoassay. On average, 24-h urinary albumin was 27.4 percent lower in space than on the ground; the difference was statistically significant. Low urinary albumin excretion could be another effect of exposure to weightlessness (microgravity).