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Hormonal and Physiological Background in the Production of B Particles by the Mouse Mammary Epithelium in Organ Cultures^*

Etienne Y. Lasfargues and Dorothy Gelber Feldman

( Department of Microbiology, Columbia University, and Rockefeller Institute for Medical Research, New York, N.Y.)

The production of B particles in organ cultures of RIII mammary glands can be influenced by hormonal stimulation. The results depend on the physiological status of the explants and the type of hormone used.

Two peaks of higher production of B particles have been observed through the pregnancy-lactation cycle of the glands: the first one, in early pregnancy, is induced by an ovarian-hypophyseal combination. It corresponds to an active alveolar differentiation and growth of the epithelium. The second, in lactation, is originated by the combined effects of two secretory inducing hormones: mammotropin and cortisol. This corresponds to a period of functional activity. In either case the formation of the B particles occurs in a phase of high protein synthesis and depends on the complete physiological integrity of the cell. The absence of hormonal stimulation or the effects of an improper combination results in the inhibition of B particles production.

Duplicate cultures of agent-free C57 mammary tissues react morphologically to the various hormone combinations in the same fashion as the RIII's; however, no B particle is formed. This is considered as further evidence that the viral particles produced in agent-positive RIII cultures might represent the milk factor.

^* Supported by U.S.P.H. grants C-4573 and C-4588 administered by Drs. M. R. Murray and D. H. Moore.

New address: Cancer Research Unit, Veterans Administration Hospital, Bronx, N.Y.

Received 6/11/62.