PMID- 12586155
OWN - NLM
STAT- MEDLINE
DCOM- 20030501
LR  - 20190906
IS  - 0045-6535 (Print)
IS  - 0045-6535 (Linking)
VI  - 51
IP  - 1
DP  - 2003 Apr
TI  - Toxicity of chlorinated phenoxyacetic acid herbicides in the experimental 
      eukaryotic model Saccharomyces cerevisiae: role of pH and of growth phase and 
      size of the yeast cell population.
PG  - 47-54
AB  - The inhibitory effect of the herbicides 2-methyl-4-chlorophenoxyacetic acid 
      (MCPA) and 2,4-dichlorophenoxyacetic acid (2,4-D) in Saccharomyces cerevisiae 
      growth is strongly dependent on medium pH (range 2.5-6.5). Consistent with the 
      concept that the toxic form is the liposoluble undissociated form, at values 
      close to their pK(a) (3.07 and 2.73, respectively) the toxicity is high, 
      decreasing with the increase of external pH. In addition, the toxicity of 
      identical concentrations of the undissociated acid form is pH independent, as 
      observed with 2,4-dichlorophenol (2,4-DCP), an intermediate of 2,4-D degradation. 
      Consequently, at pH values above 3.5 (approximately one unit higher than 2,4-D 
      pK(a)), 2,4-DCP becomes more toxic than the original herbicide. A dose-dependent 
      inhibition of growth kinetics and increased duration of growth latency is 
      observed following sudden exposure of an unadapted yeast cell population to the 
      presence of the herbicides. This contrasts with the effect of 2,4-DCP, which 
      essentially affects growth kinetics. Experimental evidences suggest that the acid 
      herbicides toxicity is not exclusively dependent on the liposolubility of the 
      toxic form, as may essentially be the case of 2,4-DCP. An unadapted yeast cell 
      population at the early stationary-phase of growth under nutrient limitation is 
      significantly more resistant to short-term herbicide induced death than an 
      exponential-phase population. Consequently, the duration of growth latency is 
      reduced, as observed with the increase of the size of the herbicide stressed 
      population. However, these physiological parameters have no significant effect 
      either on growth kinetics, following growth resumption under herbicide stress, or 
      on the growth curve of yeast cells previously adapted to the herbicides, 
      indicating that their role is exerted at the level of cell adaptation.
FAU - Cabral, M G
AU  - Cabral MG
AD  - Centro de Engenharia Biologica e Quimica, Instituto Superior Tecnico, Av. Rovisco 
      Pais, 1049-001, Lisboa, Portugal.
FAU - Viegas, C A
AU  - Viegas CA
FAU - Teixeira, M C
AU  - Teixeira MC
FAU - Sa-Correia, I
AU  - Sa-Correia I
LA  - eng
PT  - Journal Article
PT  - Research Support, Non-U.S. Gov't
PL  - England
TA  - Chemosphere
JT  - Chemosphere
JID - 0320657
RN  - 0 (Herbicides)
RN  - 0 (Soil Pollutants)
RN  - 2577AQ9262 (2,4-Dichlorophenoxyacetic Acid)
RN  - D888C394VO (2-Methyl-4-chlorophenoxyacetic Acid)
SB  - IM
MH  - 2,4-Dichlorophenoxyacetic Acid/*toxicity
MH  - 2-Methyl-4-chlorophenoxyacetic Acid/*toxicity
MH  - Dose-Response Relationship, Drug
MH  - Herbicides/*toxicity
MH  - Hydrogen-Ion Concentration
MH  - Kinetics
MH  - Models, Biological
MH  - Saccharomyces cerevisiae/drug effects/*growth & development
MH  - Soil Pollutants/*toxicity
EDAT- 2003/02/15 04:00
MHDA- 2003/05/02 05:00
CRDT- 2003/02/15 04:00
PHST- 2003/02/15 04:00 [pubmed]
PHST- 2003/05/02 05:00 [medline]
PHST- 2003/02/15 04:00 [entrez]
AID - S0045-6535(02)00614-8 [pii]
AID - 10.1016/s0045-6535(02)00614-8 [doi]
PST - ppublish
SO  - Chemosphere. 2003 Apr;51(1):47-54. doi: 10.1016/s0045-6535(02)00614-8.