Lipid composition and turnover of rough and smooth microsomal membranes in rat liver.

Subfractions of rat liver microsomes (rough, smooth I, and smooth II), isolated in a cation-containing sucrose gradient system, were analyzed. After removal of adsorbed and luminal protein, these subfractions had the same phospholipid/protein ratio, about 0.40.

Heterogeneity of rough-surfaced liver microsomal membranes of adult, phenobarbital-treated, and newborn rats.

Rough microsomes from the livers of adult, phenobarbital-treated, and newborn rats were subfractionated on a continuous sucrose gradient. Among the subfractions a marked heterogeneity in the distribution patterns of some enzyme activities appears. The isopycnic density of the various fractions in aqueous sucrose ranges from 1.

Mechanism of the cation effect in subfractionation of microsomes.

It was previously found that cations introduced into a discontinuous sucrose gradient exert a very pronounced effect on microsomal vesicles, and this principle proved to be effective in microsomal subfractionation. The mechanism of the cation effect was investigated. By using the radioactive isotopes (137)Cs and (85)Sr, it could be calculated that the amount of ions bound to the various subfractions increases their density by 0.

Biogenesis of endoplasmic reticulum membranes. I. Structural and chemical differentiation in developing rat hepatocyte.

The development of the endoplasmic reticulum of rat hepatocytes was studied during a period of rapid cell differentiation, i.e., from 3 days before to 8 days after birth.

Biogenesis of endoplasmic reticulum membranes. II. Synthesis of constitutive microsomal enzymes in developing rat hepatocyte.

The constitutive enzymes of microsomal membranes were investigated during a period of rapid ER development (from 3 days before to 8 days after birth) in rat hepatocytes. The activities studied (electron transport enzymes and phosphatases) appear at different times and increase at different rates. The increase in the enzyme activities tested was inhibited by Actinomycin D and puromycin.