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Technical Briefs |
1
Dept. of Chem. Pathol., Charing Cross & Westminster Med. Sch., London, W6 8RF, UK;
2
Dept. of Clin. Biochem., London Hosp. Med. Coll., London, E1 2AD, UK;
3
Dept. of Anesthesia, St George's Hosp. Med. Sch., Cranmer Terr., London, SW17 0RE, UK.;
4
present address: Med. Res. Council, Radiobiol. Unit, Chilton, Didcot Oxfordshire, OX11 0RD, UK;
a author for correspondence: fax (+44)-181-846-7007, e-mail b.sampson{at}cxwms.ac.uk
Surgical trauma is a stimulus for the acute-phase response (APR), which is thought to be mediated by cytokines such as interleukin-6 (IL-6) (1). Features of the APR include changes in plasma concentrations of proteins such as C-reactive protein (CRP) and albumin and a lowering of plasma Zn and Fe concentrations (2). The metallothioneins (MTs), a family of metal-binding proteins, are also likely to be increased during the APR. Indeed, MT-1 and MT-2 genes are responsive to a wide variety of stimuli, including metals, cytokines, glucocorticoid hormones, and stress (3)(4).
We previously reported a sevenfold increase in circulating MT-1 concentrations 24–48 h after elective surgery (5), confirming observations in animal experiments that MT can act as an acute-phase reactant (6)(7). We also previously showed (8) that extradural anesthesia added to general anesthesia resulted in lower concentrations of cortisol and growth hormone than did general anesthesia alone, but IL-6, CRP, and Zn concentrations did not change significantly.
Here, we have investigated the time course of the changes in plasma concentrations of MT-1, CRP, and IL-6 in patients undergoing elective surgery. We also studied the effects of extradural blockade in addition to general anesthesia. Because MT is induced by glucocorticoids (9)(10) and IL-6 (11), we examined the effects of the decreased pituitary adrenal response in extradural anesthesia on MT production.
The patients in this study, the anesthesia, and the sample collection techniques are as previously described (8). All patients gave written informed consent, and local Ethics Committee approval was obtained. Briefly, we studied 15 healthy women (ages 20–50 years) undergoing total abdominal hysterectomy for benign disease. The patients were randomized to treatment groups of extradural with general anesthesia (seven patients, receiving extradural block with local anesthetic from T4 to S5 dermatomal segments) or general anesthesia alone (eight patients). Samples of venous blood were taken immediately before the operation (zero time) and at various times during and after the operation.
MT-1 was measured by the ELISA previously described (5). The within-run CV of the assay was 12–16%, and recovery ranged from 88% to 111%; the detection limit was 5 µg/L and the reference range was <70 µg/L. IL-6 was measured by a two-site enzyme immunometric assay (Quantikine; RD Systems, British Bio-Technology, Abingdon, Oxon., UK). Intra- and interassay CVs were 7% and 9%, respectively, for an IL-6 concentration of 93 ng/L; the lower limit of detection of this assay was 3.5 ng/L. CRP was measured by latex-enhanced immunoturbidimetry (12) with an intraassay CV of <5% at all concentrations, and all samples were measured in the same assay.
Statistical significance of differences between the groups was tested by using ANOVA with repeated measures (Program 5V; BMDP Statistical Software, University of California, Berkeley, CA). The relation between CRP and MT-1 was tested by linear regression.
The time-related changes in MT-1, IL-6, and CRP in the patients are
shown in Fig. 1
. Plasma MT-1 concentrations increased in both sets of patients,
rising rapidly until 48 h after the start of anesthesia. Although
the increase appeared to be more rapid in the general anesthesia group
than in the extradural plus general group, especially at 12 h
after operation, there was no significant difference between the
groups. Similarly, concentrations of CRP increased in both groups of
patients, rising rapidly until 48 h postoperation. The correlation
between MT-1 and CRP concentrations, however, was significant
(r = 0.61, P <0.001) (not shown).
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The concentrations of IL-6 in the general anesthesia group were significantly increased at 6 h (P = 0.003), peaked at 24 h after the start of operation, and remained increased at 48 h. IL-6 concentrations also peaked at 24 h in the extradural group.
This study of MT-1 after surgery confirms that, as with CRP (2)(13), there was a delay between the start of surgery and the increase in the plasma concentration of MT-1. Between 6 and 12 h passed in both extradural and nonextradural patient groups before MT-1 concentrations began to increase. This delay between the stimulus of injury and subsequent increases in the APR is in agreement with the hypothesis that mediators such as interleukins are obligatory intermediates for the acute-phase protein response in humans.
In this study, IL-6 concentrations were increased in both groups of
patients, peaking at 24 h after operation. Differences in IL-6
concentrations between extradural and nonextradural patients were
evident at 6 h after operation, being present in lower
concentrations in the patients who also received extradural anesthesia.
Comparison of the increase in MT-1 concentration with that in IL-6 in
both nonextradural and extradural groups (Fig. 1
) suggests that the
delayed increase in IL-6 in the extradural group may affect the
increase in MT-1 in this group of patients. In particular, by 12 h
after the operation, the increase in MT-1 in the extradural group
appears to be lower than that in the control or nonextradural group;
however, this difference is not statistically significant
(P = 0.15).
The reason for induction of MT-1 during the APR is not yet clear. Given its purported role as a free radical scavenger (14), MT may play an important intracellular role as an antioxidant by removing free radicals generated by the host during tissue damage and inflammation (15), hence reducing the potential for damage. Alternatively, MT can donate Zn to apoenzymes and transcription factors (16)(17) and may thus serve as a labile source of Zn that can be utilized in many different organs to activate as-yet-unidentified metalloenzymes that are essential during the stress condition.
In conclusion, the induction of MT-1 during the APR and the observed parallel time-related responses of MT-1 and CRP suggest that the change in MT-1 is not glucocorticoid-mediated and that MT-1 and CRP respond to a similar stimulus in the APR.
References
The following articles in journals at HighWire Press have cited this article:
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  R. Gambino C-Reactive Protein—Undervalued, Underutilized Clin. Chem., November 1, 1997; 43(11): 2017 - 2018. [Full Text] [PDF]
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), n = 7 for extradural patients (
).