High resolution autoradiographic study of normal lactating mammary gland and mammary tumors of the mouse: preliminary report.

Protein metabolism of normal lactating gland and mammary tumor cells was studied with high resolution autoradiography. Special attention was devoted to the Golgi zone in both cell types because of the involvement of this structure in milk protein secretion in the normal gland cell and the topographical relation of this apparatus with viral "inclusion bodies" in the tumor. In the normal gland, the cycle of protein secretion was completed in about 50 minutes, the main part of the cycle being represented by a heavy and extensive labeling of the Golgi zone. In the tumorous gland, marking was relatively stationary and remained within the cell, the label predominating in the ergastoplasm with only a faint labeling of the Golgi apparatus. Percent markins of the nucleus was notably greater in the tumor cell as opposed to the normal gland cell. In the calculation of the specific activities of the tissues, the size of the nucleus of both cell types was very similar, while the cytoplasm of the normal gland was five times that of the tumor cell. Comparison of the specific activities showed that the over-all activity of the two cell types was not significantly different. This phenomenon supports a theory proposed by Schultze whereby the ratio of protein incorporation into the nucleus and the cytoplasm is constant and the value of this ratio decreases as the metabolic activity of the cell increases.