ABSTRACT
The effects of air pollutants such as aldehydes, ozone, nitrogen dioxide and benzene on fatty acid ω-hydroxylase activity in Vicia sativa microsomes have been investigated. Four days old etiolated V. sativa seedlings were exposed to different concentrations of selected pollutants for varying exposure times. Growing etiolated V. sativa seedlings in air containing the gaseous benzaldehyde (150 nM) led to an 8-fold enhancement of lauric acid ω-hydroxylase activity in microsomes of treated plants compared to controls grown in pure air (96 ± 10 versus 12 ± 2 pmol/min/mg protein, respectively). The induction increased with increasing gas phase concentrations (10-1300 nM) and the maximum of activity was measured after 48 h of exposure. Northern blot analysis revealed that this induction occurred via transcriptional activation of the gene coding for CYP94A1. The absence of CYP94A2 and CYP94A3 transcription activation together with the missing effect on epoxide hydrolases activities indicate the specificity of CYP94A1 induction by benzaldehyde. Exposure to nitrogen dioxide, ozone and formaldehyde also stimulated lauric acid ω-hydroxylases activity while exposure to benzene did not show any effect.
Subject(s)
Air Pollutants/toxicity , Benzaldehydes/toxicity , Cytochrome P-450 CYP4A/metabolism , Cytochrome P-450 Enzyme System/metabolism , Vicia sativa/drug effects , Blotting, Northern , Cytochrome P-450 CYP4A/biosynthesis , Cytochrome P-450 CYP4A/genetics , Cytochrome P-450 Enzyme System/biosynthesis , Cytochrome P-450 Enzyme System/genetics , Dose-Response Relationship, Drug , Enzyme Induction/drug effects , Gases , Substrate Specificity , Time Factors , Transcriptional Activation/drug effects , Vicia sativa/enzymology , Vicia sativa/geneticsABSTRACT
The purpose of this investigation was to examine changes in sarcoplasmic reticulum (SR) function in muscles subjected to different patterns of muscle activity. Frog sartorius muscles were stimulated with tetanic trains (100 ms, 100 Hz) delivered at rates of 2.0, 0.5, and 0.2 trains/s. In one set of experiments, stimulation was continued until force had declined to approximately 17% of initial (constant fatigue), whereas in the other set, stimulation was continued for 1 min (constant duration). In the constant-fatigue experiments, Ca2+ uptake (1 mM MgATP) and release rates (25 microM AgNO3, 5 mM 4-chloro-m-cresol) were depressed by similar extents following each protocol. This occurred despite 1, 4, and 17 min of stimulation, respectively, used to induce fatigue. In the constant-duration experiments, larger reductions in SR function occurred following the highest frequency stimulation protocol. These data suggest that when muscles are fatigued to similar extents, depressions in SR function are independent of the activity protocol. On the other hand, when a constant duration of activity is imposed, changes in SR function are closely linked to the extent of force reduction.