Human fibroblasts possess five distinguishable systems for amino acid transport. Initial rates for three of these normalized against cell protein decline with in vitro age. The decline most noticably affects the L system, whose rate for L-phenylalanine transport at 10 uM declines by 44% between the 27th and 39th population doubling levels. Accumulation of L-phenylalanine at 10 uM is similarly affected by age. / In spite of L system transport reduction, pool levels of L system amino acids do not decline markedly with age. The present study found the total pool for five L system amino acids (val, ileu, leu, tyr, phe) as 29 nmol mg('-1) in IMR-90-20 and 27 nmol mg('-1) in IMR-90-35. A previous study from another laboratory has reported small (15%) reductions of L system amino acids as a fraction of the total pool in high passage cells. The absence of an L system pool decline proportional to the L system transport decline is probably attributable to the high concentrations of amino acids in growth medium in comparison to the substrate concentration used in transport assays (800 uM vs. 10 uM for L-phenylalanine). / Growth of fibroblasts is relatively insensitive to pool alterations irrespective of age. Fivefold dilution of the amino acid complement of culture medium (DME) reduced L system amino acid pools about 40% in both young and old cells without significantly affecting growth. The lack of a strong age effect on amino acid pools and the additional insensitivity of older cells to reduction of the amino acid concentration of culture medium casts doubt on possible interpretation of the transport decline as a causal factor limiting growth. / Source: Dissertation Abstracts International, Volume: 46-04, Section: B, page: 1030. / Thesis (Ph.D.)--The Florida State University, 1985.
| Identifer | oai:union.ndltd.org:fsu.edu/oai:fsu.digital.flvc.org:fsu_75581 |
| Contributors | NEWTON, RANDALL BOOTH., Florida State University |
| Source Sets | Florida State University |
| Detected Language | English |
| Type | Text |
| Format | 134 p. |
| Rights | On campus use only. |
| Relation | Dissertation Abstracts International |
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