CA hypothermia rats were cooled to 30°C over 30 min and maintained for 3h followed by 1h of re-warming (). Physiological parameters (MABP, blood pH, PaO2
, and glucose) were measured (). No differences in physiologic parameters were observed before CA. Post-CA, the CA normothermia and CA hypothermia groups had an anticipated increase in PaO2
and decrease in PaCO2
) Furthermore, post-CA/hypothermia values of PaO2
in CA normothermia and CA hypothermia groups were significantly different from control (***p<0.001).
Figure 1 Time-course of rectal temperature beginning 15 min after asphyxial arrest, and ending after 3 hrs of moderate hypothermia plus 1 hr of re-warming. Control and Cardiac Arrest Normothermia rats were maintained at 37°C, and CA Hypothermia rats were (more ...)
Physiological variables in control, cardiac arrest normothermia and hypothermia rats
Effect of Cardiac Arrest and Hypothermia on 6β-hydroxytestosterone Formation Rate
, Panel A depicts the microsomal 6β-OH TST formation rate in control, CA normothermia, and CA hypothermia (n=6 per group) rats at 5h after injury. 6β-OH TST formation rates were not different between control (2388±513pmol/mg/min), CA normothermia (2374 ± 299pmol/mg/min), and CA hypothermia (2521±689pmol/mg/min) groups. , Panel B depicts the microsomal formation rate of 6β-OH TST (n=6 per group) rats at 24h after injury. 6β-OH TST formation rate was decreased in the CA normothermia compared to control rats (1484±942.9pmol/mg/min vs. 3174±965.4pmol/mg/min;*p<0.05, respectively). 6β-OH TST formation rate (4345±1198pmol/mg/min) was not different between CA hypothermia and control rats, however a difference was observed between CA hypothermia and CA normothermia rats; ‡p<0.05.
Figure 2 6β-hydroxytestosterone formation rate as a measure of CYP3A2 functional activity in liver microsomes from control, CA normothermia, and CA hypothermia treated rats. Panel A shows 6β-hydroxytestosterone formation rate in rats sacrificed (more ...)
Effect of Cardiac Arrest and Hypothermia on CYP3A2 Expression
Rats sacrificed at 5 h after injury in all three groups showed no difference in CYP3A2 mRNA expression (, Panel A and B). However, a decrease in CA normothermia group CYP3A2 mRNA expression compared to both control and CA hypothermia was observed at 24h (, Panel C and D; n=6 per group; *p<0.05). No difference was observed at 24h in the CA hypothermia rats vs control.
Figure 3 CYP3A2 mRNA hepatic expression in control, CA normothermia, and CA hypothermia rat liver. Panel A shows CYP3A2 mRNA expression at 5 h after injury. Panel B shows no difference in band density between all 3 groups(n=6). Panel C shows CYP3A2 mRNA expression (more ...)
Effect of Cardiac Arrest and Hypothermia on 6-hydroxychlorzoxazone Formation Rate
No significant difference in 6-OH CZN formation rate was observed between control (1.59±0.34nmol/mg/min), CA normothermia (1.62±0.31nmol/mg/min), and CA hypothermia (1.73±0.36nmol/mg/min) groups ( Panel A). At 24h, CA normothermia showed a significant decrease in 6-OH CZN formation rate (0.47±0.10nmol/mg/min) vs control (0.85±0.14nmol/mg/min) or CA hypothermia rats (0.93±0.36nmol/mg/min), whereas, 6-OH CZN formation rate was not different between CA hypothermia and control ( Panel B).
Figure 4 6-hydroxychlorzoxazone formation rate as a measure of CYP2E1 functional activity in liver microsomes from control, CA normothermia, and CA hypothermia treated rats. Panel A shows 6-hydroxychlorzoxazone formation rate at 5 h after injury. No differences (more ...)
Effect of Cardiac Arrest and Hypothermia on CYP2E1 mRNA Expression
Rats sacrificed at 5h after injury showed no difference in CYP2E1 mRNA expression (, Panel A and B; n=6 per group). A non-significant trend towards a decrease in CYP2E1 mRNA expression was observed at 24h between CA normothermia vs control and CA hypothermia (, Panel C and D).
Figure 5 CYP2E1 mRNA hepatic expression in control, CA normothermia, and CA hypothermia rat liver. Panel A shows CYP2E1 mRNA expression at 5 h after injury. Panel B shows no difference between groups(n=6). Panel C shows CYP2E1 mRNA expression at 24 h after injury. (more ...)
Effect of Cardiac Arrest and Hypothermia on the Expression of Pregnane X Receptor (PXR) Target Genes
The mRNA expression of an organic anion transporter (Oatp2), UDP- glucuronosyltransferase (UGT1A1), and two CYP genes that are known to have common regulatory control by the pregnane X receptor were evaluated in the rat liver. depicts the mRNA expression of Oatp2, UGT1A1, CYP3A2, and CYP2C2 in the liver from control, CA normothermia, and CA hypothermia rats. A significant reduction in mRNA expression of Oatp2, CYP3A2, and CYP2C2 was observed in CA normothermia as compared to control animals. The expression of Oatp2, UGT1A1, CYP3A2, and CYP2C2 was increased in rats that received hypothermia after CA vs normothermia.
Figure 6 Expression levels of PXR target genes were evaluated to determine the effect of CA and hypothermia on drug metabolism and detoxification pathways. Real-time PCR analyses of liver RNA levels were determined from control, CA normothermia, and CA hypothermia (more ...)
Effect of Cardiac Arrest and Hypothermia on IL-6 Concentrations in Rat Plasma
depicts the time-course of plasma concentrations of IL-6 in 3 treatment groups, control, CA normothermia, and CA hypothermia; n=6 per group. CA normothermia produced increases in IL-6 concentrations compared to control at 60, 70, and 90min after injury;***p<0.001. When hypothermia was applied in the CA model, the rise in IL-6 plasma concentrations was attenuated and did not differ from control.
Figure 7 Plasma IL-6 levels in control, CA normothermia, and CA hypothermia after injury. CA normothermia IL-6 plasma concentrations at 60, 70, and 90 min after injury were significantly increased as compared to control or CA hypothermia (***p<0.001). (more ...)
Effect of IL-6 on hPXR Expression of CYP3A2 in HepG2 Cells
depicts the dose dependent effect of IL-6 on luciferase reporter plasmid expression in the presence and absence of rifampin. Data demonstrates that IL-6 (1 unit — 100 units) significantly inhibits both the basal and inducible expression of the PGL3-rCYP3A2-Luc natural promoter. An IL-6 dose dependent reduction in luciferase activity was observed in both vehicle control and rifampin induced expression of the natural promoter.
Figure 8 Co-transfection of hPXR and pGL3-rCYP3A2 natural promoter treated by human IL6 in HepG2 cells showed suppression of PXR activation. HepG2 cells were cotransfected with 1.4kb natural promoter pGL3-rCYP3A2-Luc reporter and human PXR. Transfected cells were (more ...)