DNA synthesis in mouse epidermis: S phase cells that remain unlabeled after pulse labeling with DNA precursors progress slowly through S

Journal Article · Thu Dec 01 04:00:00 EST 1983 · J. Invest. Dermatol.; (United States)

DOI:https://doi.org/10.1111/1523-1747.ep12523189· OSTI ID:7017260

Clausen, O P; Elgjo, K; Kirkhus, B; Pedersen, S; Bolund, L

Epidermal basal cells from hairless mice were isolated after pulse labeling with tritiated DNA precursors and subjected to DNA flow cytometry combined with cell sorting. Cells were sorted from a window in the middle of the S phase, collected on glass slides, and subjected to autoradiography. Unlabeled cells in the middle of the S phase were found in normal mouse epidermis after optimal pulse labeling with tritiated thymidine ((/sup 3/H)dThd), in accordance with previous results. The proportion of unlabeled S phase cells was considerably increased among basal cells from mice treated with growth-inhibitory epidermal extracts. Reanalysis and re-sorting of cells previously sorted from mid S showed that unlabeled cells could not be accounted for by G1 contamination. Furthermore, labeling with precursors incorporated into DNA by ''de novo'' metabolic pathway ((/sup 3/H)Urd) did not reduce the proportion of unlabeled S phase cells, either when given alone or when given in combination with the precursor for DNA incorporated by the ''salvage'' pathway ((/sup 3/H)dThd). This strongly indicates that the unlabeled S phase cells do not synthesize DNA continuously, or are synthesizing DNA at a rate below the level of detection. A reduced proportion of unlabeled S phase cells was found in regenerating epidermis. This may be explained by a dilution effect caused by the 3-fold increase in the total number of cells within S phase at this condition. The observation that essentially all cells in mid S phase were labeled during 4 days of continuous labeling with (/sup 3/H)dThd, indicates that cells in S phase that remain unlabeled after optimal pulse labeling are cycling, albeit slowly. Two-parameter sorting based on DNA and light scatter indicated that slowly cycling cells are larger than the average. These cells may represent a subpopulation of basal cells going through their last division cycle before differentiation.

• Research Organization: Rikshospitalet, Oslo, Norway
• OSTI ID: 7017260
• Journal Information: J. Invest. Dermatol.; (United States), Journal Name: J. Invest. Dermatol.; (United States) Vol. 81:6; ISSN JIDEA
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
ANIMAL CELLS
ANIMALS
AUTORADIOGRAPHY
AZINES
BIOCHEMICAL REACTION KINETICS
BIOLOGICAL PATHWAYS
BIOSYNTHESIS
BODY
CELL CYCLE
CELL FLOW SYSTEMS
DNA
HETEROCYCLIC COMPOUNDS
ISOTOPE APPLICATIONS
KINETICS
LABELLED COMPOUNDS
MAMMALS
MICE
NUCLEIC ACIDS
NUCLEOSIDES
NUCLEOTIDES
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANS
PYRIMIDINES
REACTION KINETICS
RIBOSIDES
RODENTS
SKIN
SYNTHESIS
THYMIDINE
TRACER TECHNIQUES
TRITIUM COMPOUNDS
VERTEBRATES