Limited Penetration of Perfluorocarbon in Porcine Pancreas Preserved by Two-Layer Method with ¹⁹Fluorine Magnetic Resonance Spectroscopy and Headspace Gas Chromatography

Abstract

The mechanism of the two-layer method (TLM) of pancreas preservation is unclear. Facilitating oxygen diffusion into preserved pancreas has been suggested, but direct measurements of tissue pO 2 have yielded conflicting results. The degree of penetration of perfluorocarbon (PFC) into the pancreas during TLM storage is unknown. Segments of porcine pancreas (7.5 cm in length) were preserved either in University of Wisconsin solution (UW) alone (n = 6) or in TLM for 24 h (n = 6). Pancreatic samples were analyzed using Varian INOVA 9.4T MR scanner. External PFC standard was introduced for quantification. Four consecutive transverse images of 4 mm thickness were obtained using a spin-echo sequence. 19 Fluorine magnetic resonance spectroscopy ( 19 F MRS) was performed with the same parameters except with more averages. MR data were confirmed by headspace chromatography. PFC standard was readily detected in 19 F MR images. There was no signal from pancreas in 19 F MR images following either UW or TLM storage.19 F MR spectra typical of PFC were not obtained from either UW-or TLM-preserved pancreas with nonlocalized 19 F MRS. Mean concentration of PFC in TLM pancreas measured by head space chromatography was 0.011 nl/g (SD ±0.006), not significantly different from background concentration (0.012 nl/g, SD ±0.006) in UW pancreas (p = 0.42). There was no evidence of penetration of PFC into pancreas tissues investigated either by MR or chromatography in organs preserved at hypothermia by TLM, and mechanisms of TLM remain speculative.

Hyperbaric oxygenation of UW solution positively impacts on the energy state of porcine pancreatic tissue*

“…Therefore, the hypothesis of a physiological effect mediated by improved gas transfer into a solid pancreas and the mechanisms improving ATP levels remain unclear [16]. It has been shown that there were no significant differences in ATP content in pancreatic tissue after preservation when comparing TLM to simple cold UW organ preservation [16]. Moreover, a recent study showed that TLM did not improve the preservation condition of porcine kidneys [17].…”

“…There is no evidence of penetration of the PFC into large-animal pancreatic tissue preserved by TLM. Therefore, the hypothesis of a physiological effect mediated by improved gas transfer into a solid pancreas and the mechanisms improving ATP levels remain unclear [16]. It has been shown that there were no significant differences in ATP content in pancreatic tissue after preservation when comparing TLM to simple cold UW organ preservation [16].…”

“…Organ storage in Celsior + revealed AMP levels of 0.18 ± 0.01 nmol/mg protein, whereas pancreatic tissue preserved in HTK contained 0. 16 Statistical analysis of the different groups in terms of nucleotide levels revealed that the use of UW þ HBO for pancreas preservation resulted in significantly higher amounts of nucleotides when compared to UW, HTK, Celsior + as well as Celsior + þ HBO (p < 0.05). Comparison of the different preservation solutions with or without pre-oxygenation showed a significant positive impact of pre-oxygenation in terms of AMP, ADP and ATP levels in organs stored in UW þ HBO (p < 0.02).…”

“…Recently it has also been shown that the TLM only oxygenates [15,16] a small volume fraction of the pancreas and therefore does not provide oxygen to all islet cells located in the organ. Moreover, the use of TLM has shown no superiority over conventional organ storage in kidneys [17].…”

Blood monitoring of perfluorocarbon compounds (F-tert-butylcyclohexane, perfluoromethyldecalin and perfluorodecalin) by headspace-gas chromatography-tandem mass spectrometry

“…Nevertheless, despite their relatively high molecular weight, PFCs constitute volatile compounds. Therefore, headspace extractions have rapidly become the technique of choice for these molecules and have reduced the time of extraction and analysis, increasing the operator safety through the automisation of the device [28][29][30][31].…”