Extracellular regulation of fibroblast multiplication: A direct kinetic approach to analysis of role of low molecular weight nutrients and serum growth factors

Abstract

Factors 12946The principles of enzyme kinetic analysis were applied to quantitate the relationships among serum-derived growth factors, nutrients, and the rate of survival and multiplication of human fibroblasts in culture. The survival or multiplication rate of a population of cells plotted against an increasing concentration of a growth factor or nutrient in the medium exhibited a hyperbolic pattern that is characteristic of a dissociable, saturable interaction between cells and the ligands. Parameters equivalent to the Km and Vm, of enzyme kinetics were assigned to nutrients and growth factors. When all nutrient concentrations were optimized and in steady state, serum factors accelerated the rate of multiplication of a normal cell population. The same set of nutrients that supported a maximal rate of multiplication in the presence of serum factors supported the maintenance of non-proliferating cells in the absence of serum factors. Therefore, under this condition, serum factors are required for cell division and play a purely regulatory role in multiplication of the cell population. The quantitative requirement for 18 nutrients of 29 that were examined was significantly higher (P < 0.001) for cell multiplication in the presence of serum factors than for cell maintenance in the absence of serum factors. This indicated specific nutrients that may be quantitatively important in cell division processes as well as in cell maintenance. The quantitative requirement for CaZ+, Mg2+, K+, Pi, and 2-oxocarboxylic acid for cell multiplication was modified by serum factors and other purified growth factors. The requirement for over 30 other nutrients could not clearly be related to the level of serum factors in the medium. Serum factors also determined the Ca2+, K+, and 2-oxocarboxylic acid requirement for maintenance of non-proliferating cells. Therefore, when either Cazf, K+, or 2-oxocarboxylic acid concentration was limiting, factors in serum played a role as cell "survival or maintenance" factors in addition to Abbreviations: N-HLF, normal human lung fibroblasts; SV-HLF, human lung fibroblasts transformed with SV40 virus; EGF, epidermal growth factor; MCDB 100, a series of nutrient media formulas developed for human diploid fibroblasts; FBSP, fetal bovine serum proteins; So.,,, the substrate or ligand concentration that promotes a half-maximal rate of cell survival or multiplication; Rma,, the maximal rate of cell multiplication.

Application of flow cytometric cell cycle analysis to the assessment of condition and growth in larvae of a freshwater teleost Galaxias olidus

“…5). This might be attributable to the lag in resynthesising polypeptide growth factors, which are thought to stimulate cell division by modifying the response of normal cells to nutrients (McKeehan and McKeehan 1981;Baserga 1985). Alternatively, this lag may be associated with impairment of digestive ability (e.g., Tyler 1970) and reduced food intake (e.g., Bilton and Robbins 1973), which have been recorded in fish after periods of starvation.…”

“…Certain nutrients are qualitatively more important in cell division and maintainance (Mckeehan and Mckeehan 1981), and the diet of the fish may influence the cell cycle and the interpretation of the sensitivity of the FCA. Wild G. olidus larvae have a diet consisting of aquatic and terrestrial invertebrates (Close 1995), while aquarium larvae were reared on a diet of brine shrimp.…”

“…The G1 phase contains a "restriction point" (R), the progression through which depends on adequate nutrition (e.g., amino acid supply) and serum factors. Essential amino acids provided from the diet are critical for initiation and continuation of the cell cycle due to their role in the formation of proteins involved in DNA replication (Eagle 1955;Mckeehan and Mckeehan 1981;Baserga 1985). The cell cycle has protective mechanisms that prevent lack of nutrients from stalling the cell cycle during critical periods such as DNA synthesis (Murray and Hunt 1993).…”

Mathematical Model for the Effects of Epidermal Growth Factor Receptor Trafficking Dynamics on Fibroblast Proliferation Responses

“…Some investigators have applied the simple Monod model for the dependence of the specific cell growth rate, p, on serum concentration (Glacken et al, 1988). McKeehan and McKeehan (1981) offered a similar model to relate cell growth rate to the concentration of specific growth serum components in empirical fashion.…”

Metabolic Approaches to Cancer Cachexia

“…Weinhouse has suggested (132) that this may account for the fact that glycolysis does not stop when the cells are exposed to oxygen, and thus may help explain some of Warburg's observations. Furthermore, pyruvate may play a role in the regulation of cell proliferation beyond its participation in glycolysis (86). The McKeehans ' work, men tioned above, suggests that the extracellular concentration of pyruvate and its interaction with serum factors may be important in the regulation of cell division in normal human lung fibroblasts.…”