[Alterations of the volume and surface of liver cells of male rats during postnatal development].

To characterize the postnatal development of hepatocytes of male rats quantitative, morphometrical investigations of male rat livers were carried out at the following times: day of birth, 1st, 2nd, 3rd, 4th, 5th, 6th, 7th, 14th, 21st, and 28th day as well as 2nd, 3rd, 4th, 5th, and 6th month. Several methods were used to determine the cell volumes and surfaces as a whole, the nucleus, and the sinusoidal (supranuclear), lateral, and bile cancliculi-near cellular zone, as well as the sinusoidal, lateral, and bile canaliculi-near plasma membrane. The cellular volume increases from the day of birth (5,775.9 +/- 545.5 micrometer 3) till the 6th month to 11,494.2 +/- 1,241.6 micrometer 3. At the same time, the liver cell surface increases from 1,900 micrometer 2 to 3,191.7 micrometer 2. The number of microvilli of the sinusoidal plasma membrane increases from 1,074.4 to 2,170.0, and of the plasma membrane limiting the bile canaliculi their number changes from 248.9 to 340.2. The values of the liver volumes and surfaces of adult animals differ from those in the literature, as they are based on mononuclear cells only (i.e., the about 30% binuclear cells are not taken into account) and a smooth surface without considering the existence of microvilli. The nuclear volumes increase from 412.7 +/- 28.2 micrometer 3 (birth) to 549.5 +/- 440 micrometer 3, whereas the relative percentage decreases from 7.14% to 4.78%, which corresponds with the findings of other authors. The proportion of the 3 zones of the cytoplasm changes in the following way : day 0 (birth) : sinusoidal zone: 2,224 micrometer 3 = 36.8%; lateral zone: 1,473 micrometer 3 = 25.9%; bile canaliculi-near zone: 1,017 micrometer 3 = 17.7%; end of 6th month : sinusoidal zone: 4,000 micrometer 3 = 34.8%; lateral zone: 4,724 micrometer 3 = 40.0%; bile cancliculi-near zone: 1,345 micrometer 3 = 12.1%. Taking into account other findings our investigations suggest that the postnatal development of the male rat liver can be definitely characterized by determining the parameters at the following dates: day of birth, 3rd, 4th, 5th, 7th, 14th, and 28th day, 3rd and 6th month.