Effect of cyclosporine on hepatic energy status and on fructose metabolism after portacaval shunt in dog as monitored by phosphorus-31 nuclear magnetic resonance spectroscopy in vivo

Abstract

The effect of cyclosporin A on the hepatic energy status and intracellular pH of the liver and its response to a fructose challenge has been investigated using in vivo phosphorus-31 nuclear magnetic resonance spectroscopy in dogs. Three experimental groups were studied: (a) control dogs (n = 5), (b) dogs 4 days after the creation of an end-to-side portacaval shunt (n = 5), and (c) dogs 4 days after portacaval shunt and continuous infusion of cyclosporin A (4 mg/kg/day) by way of the left portal vein (portacaval shunt plus cyclosporin A, n = 5). The phosphorus-31 nuclear magnetic resonance spectra were obtained at 81 MHz using a Bruker BIOSPEC II 4.7-tesla nuclear magnetic resonance system equipped with a 40-cm horizontal bore superconducting solenoid. The phosphomonoesters (p less than 0.01), inorganic phosphate and ATP levels (p less than 0.05) were decreased significantly in portacaval shunt-treated and in portacaval shunt-plus-cyclosporin A-treated dogs compared with unshunted control dogs. After a fructose challenge (750 mg/kg body wt, intravenously), fructose-1-phosphate metabolism was reduced in portacaval shunt-treated dogs compared with either the normal or portacaval shunt-plus-cyclosporin A-treated dogs (p less than 0.05). Both portacaval shunt- and portacaval shunt-plus-cyclosporin A-treated dogs demonstrated a reduced decline in ATP levels after fructose infusion when compared with the controls (p less than 0.05). Immediately after the fructose challenge, the intracellular pH decreased from 7.30 +/- 0.03 to 7.00 +/- 0.05 in all animals (p less than 0.01) and then gradually returned to normal over 60 min.(ABSTRACT TRUNCATED AT 250 WORDS)

Fig. 1

In vivo ³¹P-NMR spectra of dog liver in normal dog liver (control) 4 days after PCS and 4 days after PCS plus continuous infusion of CsA in the left portal vein branch (PCS + CsA). Peak assignments: (1) MDPA; (2) PM; (3) Pi; (4) PD; (5) γ-ATP plus β-ADP; (6) α-ATP plus α-ADP; and (7) β-ATP. These spectra consisting of 64 acquisitions were accumulated in 4 min with a ∼3 sec pulse delay (respiratory cycle) and 90-degree pulse. MDPA was used as the external reference standard for chemical shift and for intergroup and intragroup relative concentration measurements.

Fig. 2

Relative phosphate metabolite concentrations in dog liver. The relative concentrations of phosphate metabolites in the liver were measured by dividing the integrated area under each peak by the MDPA area used as an external reference in each experiment. The n value for each group was 5. The values of the columns marked with asterisks are significantly different from the values of the other columns (*p < 0.05, **p < 0.01).

Fig. 3

Effect of a fructose challenge on the in vivo ³¹P-NMR spectrum of normal dog liver. Spectra obtained before fructose (a) and 8 min after fructose administration (b) administered at a dose of 750 mg/kg body wt intravenously as a bolus. The difference spectrum is labeled (b-a).

Fig. 4

F-1-P levels in dog liver after a fructose challenge. The time course of F-1-P levels in dog liver in the three groups of dogs (control, n = 5; PCS, n = 5; PCS + CsA, n = 5) after a fructose load (750 mg/kg body wt administered intravenously as a 30% solution in saline, over 2 min, beginning at 0 time). Values are shown as relative changes from basal value at 0 time for the PM area relative to the MDPA area, mean ± S.E.M. The asterisk denotes p < 0.05.

Fig. 5

ATP levels after a fructose challenge. The time course of intrahepatic ATP levels in three groups of dogs (control, n = 5; PCS, n = 5; PCS + CsA, n = 5) after a fructose load (750 mg/kg body wt administered intravenously as a 30% solution in saline, over 2 min, beginning at 0 time). Values are relative changes from the basal value at 0 time for the β-ATP area relative to the MDPA area, mean ± S.E.M. The asterisk (*) denotes p < 0.05.