Monoclonal antibodies to α₂(u)-globulin and immunocytofluorometric analysis of α₂(u)-globulin-synthesizing hepatocytes during androgenic induction and aging

Stable hybridomas generated by fusion of spleen cells from hyperimmunized mice and mouse myeloma cells were cloned to prepare monoclonal antibodies to α₂(u)-globulin, an androgen-dependent urinary protein of hepatic origin. One of these monoclonal antibodies was used as a probe for immunocytofluorometric analysis of α₂(u)-globulin producing hepatocytes during androgenic induction and aging through fluorescence-activated cell sorting (FACS). FACS patterns of hepatocytes from mature male rats that produce high levels of α₂(u)-globulin showed two distinct peaks, arbitrarily designated as peak I (weakly fluorescent) and peak II (brightly fluorescent). In the mature male rat, peak II represented about 40% of the total hepatocytes, and the fluorescence intensity of this subpopulation decreased in direct correspondence with the gradual decline of α₂(u)-globulin synthesis during aging. Similarly the andrenogenic induction of this protein in ovariectomized female rats was associated with an increase in the fluorescence intensity of the hepatocyte subpopulation under peak II rather than an increase in the relative number of these cells. From these results we conclude that the androgen-dependent synthesis of α₂(u)-globulin and its alteration during aging are confined to a specific subpopulation of hepatocytes within the liver.