Modifications in some rat liver cell components following stimulation with isoprenaline (a cytospectrophotometric,...

The liver cell is a quite interesting model for the study of several cytophysiological problems. Proper suspensions of isolated liver cells can be obtained which can be conveniently studied by means of quantitative microtechniques. Several cytochemical and cytophysical techniques (cytospectrophotometry, microrefractometry, and cytoelectrophoresis) were employed for elucidating the effects on the stimulation of the liver cell with high doses of isoprenaline, an amine which is known to produce hypertrophy and hyperplasia in various organs with effects also at the genetic and metabolic level. The following data were collected during the postnatal development of rats up to the 70th day of life: 1) DNA content per nucleus; 2) total dry mass per cell; 3) cellular electrophoretic mobility in connection with the sialomucinic component of the membrane. The process of polyploidization of the liver cell (typical of this life period) was generally accelerated; in this connection, an early appearance of binucleate cells and subsequent significative variations in their incidence were observed. This fact is important as the binucleate cells should represent an alternative intermediate step in the polyploidization phenomenon. At the same time, marked, although transient, signs of cellular hypertrophy were detected during a rearrangement of the hepatocyte dry mass, where the values tended to a multimodal distribution; in particular, IPR appeared to favor the disappearance of cells with a lower mass to the advantage of those with an intermediate mass. The study of electrophoretic mobility evidenced the role of the sialomucinic component of the membrane in the changes occuring in the parenchyma: indeed, this component exhibited an increase, thus causing an acceleration of the mobility similar to the one observed in actively proliferating cell populations. Such change persists even long after the IPR stimulus has ended and, at any rate, beyond the immediate phase of DNA synthesis and the appearance of binucleate cells.