Studies on the persistence of differentiated functions in rat hepatocytes set into primary tissue culture. II. Production of specific exportable proteins and the effect of purine cyclic nucleotides: an immunofluorescent study.

Immunofluorescent studies showed that even after 15 days in vitro primary neonatal rat hepatocytes contained in their cytoplasm detectable amounts of different adult rat serum proteins, including fibrinogen and proalbumin. Estimation of the intensity of specific fluorescence revealed that in untreated cultures the hepatocytic content of the various exportable antigens progressively diminished between the 5th and 15th day in vitro. Treatment with cAMP (10(-5) M daily) alone increased in hepatocytic cytoplasm, with respect to parallel controls, the content of total exportable proteins and of proalbumin. Daily administration of an equimolar association (10(-5) M) of cAMP with cGMP increased the total protein, proalbumin and fibrinogen content of hepatocytes. Daily treatment with cGMP (10(-5) M) alone caused only light and transitory increases in the content of proalbumin and fibrinogen. Rocket immune electrophoresis showed that the hepatocytic secretion of specific proteins into the growth medium persisted up to the 15th day, although progressively diminishing in intensity. The secretion of total exportable proteins and of albumin, but not of fibrinogen, was stimulated by cGMP used alone or coupled with equimolar cAMP.