Secretory γA in normal urine

Abstract

The physicochemical nature of γA was investigated in normal male and female urine concentrated approximately 1000 times. Sucrose density gradient ultracentrifugation and Sephadex G-200 chromatography revealed that urinary γA has sedimentation properties intermediate between 19S and 7S molecules. Isolation of urinary γA by DE 52 chromatography free of other immunoglobulins with subsequent antigenic analysis showed that the urinary γA-molecule is antigenically indistinguishable from the γA-molecules found in other external secretions and has a corrected sedimentation coefficient of 11.8S. In addition, like other secretory γA-molecules and unlike serum polymeric γA, urinary γA resisted mild reductive measures with 0.1M β-mercaptoethanol. Free or unattached secretory “piece” was found in all normal urines tested and in agammaglobulinemic urine. Secretory “piece” antigenic determinants were also found in ureteric urine. The average daily excretion of urinary γA was 1.1 mg. The maximum excretion of urinary 7S γG per 24 hr was approximately 3 mg.