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Effect of vasodilators on hepatic microcirculation: Inhibition of norepinephrine induced vasoconstriction in the isolated perfused rat liver
318
STUDIES ON BILE ACID GLUCOSIDES IN HUMAN BILE AND URINE
H.-U. Marschall, B. Eqestad, E. Matern*, S. Matern*, and J. Sj6vall Dept. of Physiol. Chem., Karolinska Instituter, S-I0401 Stockholm and *Abt. Inhere Medizin IIl des Klinikums der RWTH, D-5100 Aachen The formation of bile acid glucosides was recently shown to be a novel conjugation mechanism of bile acids in vitro as well as in vivo. A glucosyltransferase catalyzing the conjugation of bile acids with glucose could be isolated from human liver microsomes (Proc. Natl. Acad. Sci. USA, 81, 7036-7040, 1984). Gas chromatography/mass spectrometry (GC/MS) of methyl ester trimethylsilyl ether derivatives indicated the excretion of glucosides of hyodeoxycholic (HDCAgluc), ursodeoxycholic (UDCAgluc), deoxycholic (DCAgluc), chenodeoxycholic (CDCAgluc) and cholic (CAgluc) acids and of glycine (GCAgluc) and taurine (TCAgluc) conjugated chenodeoxycholic and cholic acids in urine of healthy volunteers (FEBS letters 213, 411-414, 1987). In order to get more detailed structural informations, oxidative cleavage of the glucosidic linkage of CDCAgluc and HDCAgluc as well as of urinary unconjugated bile acid glucosides was performed with sodium periodate. The unusual order of elution of HDCAgluc at shorter retention times than CDCAgluc can be explained by the former being conjugated at the 6~- and the latter at the 3=-position, as was already found by the structural studies of the respective bile acid glucuronides. The investigations on the occurrence of these new bile acid conjugates were extended to bile obtained from patients undergoing gallstone surgery. After extracting the bile acids with Sep-Pak C cartridges from bile diluted with 0.5 M triethyl. ammonzum
sulphate,
pH
7.2,
a t 64
O
18
.
C, g r o u p s e p a r a t z o n was p e r f o r m e d by c h r o m a t o g r a p h y on
Lipidex-DEAP. GC/MS analysis was performed with the fractions of unconjugated, and of glycine and taurine conjugated bile acids after treatment with cholylglycine hydrolase and rechromatography. Peaks were found with retention times and fragmentation patters similar to those described for bile acid glucosides derived from human urine.
319
EFFECT OF VASODILATORS ON HEPATIC MICROCIRCULATION:INHIBITION OF NOREPINEPHRINE INDUCED VASOCONSTRICTION IN THE ISOLATED PERFUSED RAT LIVER Ph. MARTEAU, F. BALLET, Y. CHRETIEN, C. REY, R. POUPON. Unit4 d'H4patologie INSERM HSpital Saint-Antoine, Paris, France
Norepinephrine (NE) is a potent vasoconstrictor of the hepatic microvasculature. In cirrhosis and stressfull states, abnormalities of liver perfusion could be in part secondary to the high levels of circulating NE. In these situations, the use of agents with vasodilatory properties on hepatic microcirculation could improve liver perfusion and presumably liver function. We studied the effects of a series of vasodilators on the intrahepatic vasoconstriction induced by NE in the isolated perfused rat liver. Livers were perfused at a constant pressure (P), the measured variable was portal blood flow (Q) and intrahepatic portal resistance (R) was calculated as R = P/Q. R was increased by administration of NE (10-~M) and increasing doses of vasodilator were administered from I~7to I~3M. The vasodilatory potency was determined from the molar concentration which induced a 50% inhibition of R (IDS0) Ifenprodil (2.17x10-6M), phentolamine (3.03 x 10-6M), isoxsuprine (3.05 x I0-6M), clonidine (3.27 x IO~M), sodium nitroprusside (1.53 x I0-5M) and buflomedil (5.61 x I0-5M) had a high potency. Diazoxide, papaverine, pentoxifylline and trinitrine had a weak potency. Verapamil, diltiazem, propranolol, isoproterenol, naftidofuryl, vincamine and cinepazide were ineffective. In conclusion, different classes of pharmacological agents have significant vasodilatory properties on the hepatic microvasculature, some of them at concentrations in the therapeutic range.
$165
STUDIES ON BILE ACID GLUCOSIDES IN HUMAN BILE AND URINE
H.-U. Marschall, B. Eqestad, E. Matern*, S. Matern*, and J. Sj6vall Dept. of Physiol. Chem., Karolinska Instituter, S-I0401 Stockholm and *Abt. Inhere Medizin IIl des Klinikums der RWTH, D-5100 Aachen The formation of bile acid glucosides was recently shown to be a novel conjugation mechanism of bile acids in vitro as well as in vivo. A glucosyltransferase catalyzing the conjugation of bile acids with glucose could be isolated from human liver microsomes (Proc. Natl. Acad. Sci. USA, 81, 7036-7040, 1984). Gas chromatography/mass spectrometry (GC/MS) of methyl ester trimethylsilyl ether derivatives indicated the excretion of glucosides of hyodeoxycholic (HDCAgluc), ursodeoxycholic (UDCAgluc), deoxycholic (DCAgluc), chenodeoxycholic (CDCAgluc) and cholic (CAgluc) acids and of glycine (GCAgluc) and taurine (TCAgluc) conjugated chenodeoxycholic and cholic acids in urine of healthy volunteers (FEBS letters 213, 411-414, 1987). In order to get more detailed structural informations, oxidative cleavage of the glucosidic linkage of CDCAgluc and HDCAgluc as well as of urinary unconjugated bile acid glucosides was performed with sodium periodate. The unusual order of elution of HDCAgluc at shorter retention times than CDCAgluc can be explained by the former being conjugated at the 6~- and the latter at the 3=-position, as was already found by the structural studies of the respective bile acid glucuronides. The investigations on the occurrence of these new bile acid conjugates were extended to bile obtained from patients undergoing gallstone surgery. After extracting the bile acids with Sep-Pak C cartridges from bile diluted with 0.5 M triethyl. ammonzum
sulphate,
pH
7.2,
a t 64
O
18
.
C, g r o u p s e p a r a t z o n was p e r f o r m e d by c h r o m a t o g r a p h y on
Lipidex-DEAP. GC/MS analysis was performed with the fractions of unconjugated, and of glycine and taurine conjugated bile acids after treatment with cholylglycine hydrolase and rechromatography. Peaks were found with retention times and fragmentation patters similar to those described for bile acid glucosides derived from human urine.
319
EFFECT OF VASODILATORS ON HEPATIC MICROCIRCULATION:INHIBITION OF NOREPINEPHRINE INDUCED VASOCONSTRICTION IN THE ISOLATED PERFUSED RAT LIVER Ph. MARTEAU, F. BALLET, Y. CHRETIEN, C. REY, R. POUPON. Unit4 d'H4patologie INSERM HSpital Saint-Antoine, Paris, France
Norepinephrine (NE) is a potent vasoconstrictor of the hepatic microvasculature. In cirrhosis and stressfull states, abnormalities of liver perfusion could be in part secondary to the high levels of circulating NE. In these situations, the use of agents with vasodilatory properties on hepatic microcirculation could improve liver perfusion and presumably liver function. We studied the effects of a series of vasodilators on the intrahepatic vasoconstriction induced by NE in the isolated perfused rat liver. Livers were perfused at a constant pressure (P), the measured variable was portal blood flow (Q) and intrahepatic portal resistance (R) was calculated as R = P/Q. R was increased by administration of NE (10-~M) and increasing doses of vasodilator were administered from I~7to I~3M. The vasodilatory potency was determined from the molar concentration which induced a 50% inhibition of R (IDS0) Ifenprodil (2.17x10-6M), phentolamine (3.03 x 10-6M), isoxsuprine (3.05 x I0-6M), clonidine (3.27 x IO~M), sodium nitroprusside (1.53 x I0-5M) and buflomedil (5.61 x I0-5M) had a high potency. Diazoxide, papaverine, pentoxifylline and trinitrine had a weak potency. Verapamil, diltiazem, propranolol, isoproterenol, naftidofuryl, vincamine and cinepazide were ineffective. In conclusion, different classes of pharmacological agents have significant vasodilatory properties on the hepatic microvasculature, some of them at concentrations in the therapeutic range.
$165