0.61 Epinephrine increases metabolic clearance rate of basal and infused amino acids in man

Abstract

transmembrane transport might be facilitated by binding taurine to a suitable carrier. Aim: To investigate uptake (mode, site and extent) and utilization of vascularly supplied synthetic taurine conjugates, L-alanyltaurine (Ala-Tau), L-phenylalanyltaurine (Phe-Tau) and L-tyrosyltaurine (Tyr-Tau). Experimental: Small intestine from anaesthetized rats (n = 20, male 250-350g) was isolated following cannulation of the superior mesenteric artery and the portal vein. Perfusion was carried out over 60 min in vascular and luminal (5, 0.5 ml/min, resp.) single pass technique. Ala-Tau, Phe-Tau,Tyr-Tau or taurine were added (0.15mM) to vascular perfusion medium (fluorocarbon emulsion in Henseleit buffer). Tyr-Tau perfusions were carried out with and without peptidase inhibitors bestatin or amastatin (5 ~M, each). Control perfusions without addition of the conjugates served as baseline. Sampling and analysis: Arterial/venous and luminal aliquots were taken every 5-10min for measurement of amino acids (AA)/conjugates (RP-HPLC). Flux rates were calculated from arteriovenous concentration differences (mean 0-60 rain) considering g organ dry weight (DW). Metabolic control (pO2, glucose/lactate handling, pH) revealed undisturbed viability during the investigation. Results: During single pass perfusion all taurine conjugates were extracted from vascular perfusate accompanied with liberation of the constitutent amino acids (Table). Peptidase inhibitors bestatin and amastatin decreased markedly yet incomplete the extraction (-66 and -54 nmol/min/g DW, resp. vs -204 nmol/min/g DW). Importantly, control or free taurine perfusions did not result in differences in vascular liberation of taurine.