Effects of the perfusion of beta-, beta2-, or beta3-adrenergic agonists or epinephrine on in situ adipose tissue lipolysis measured by microdialysis in underfed ewes.

The effects of isoproterenol (ISO, a non-selective beta-agonist), terbutaline (TER, a selective beta2-agonist), CL316243 (CL, a selective beta3-agonist), and epinephrine (EPI, beta- and alpha2-agonist) on in situ lipolytic response of s.c. adipose tissue were investigated in vivo, using a microdialysis method to measure glycerol release, in 12 adult nonlactating and ovariectomized, underfed Lacaune ewes. All the adrenergic compounds were perfused for 120 min at 10(-6), 10(-5), and 10(-4) M. They had no lipolytic effect at 10(-6) M. Isoproterenol and EPI at 10(-5) and 10(-4) M enhanced, in the same way, maximal response and area under the concentration curve (AUC) of dialysate glycerol, thus suggesting that involvement of alpha2-adrenoceptors in the control of in situ lipolysis is of minor importance in underfed ewes. Terbutaline had only a slight lipolytic effect at 10(-5) M. This low effect could be due to a lower affinity of TER than of ISO for the beta2-adrenoceptors. The beta3-agonist, CL, had no lipolytic effect whatever the concentration perfused. Further studies are needed to prove the putative presence of beta3-adrenoceptors and their possible role in the ovine adipose tissue.

Amino acid determination in biological fluids by automated ion-exchange chromatography: performance of Hitachi L-8500A.

The Hitachi L-8500A is a newly available apparatus for amino acid (AA) analysis that allows automatic on-line mixing of the ninhydrin reagent. The within-run precision (human plasma pools at three different concentrations) showed CVs < 3.8% except for the lowest concentration of citrulline (4.4%), Tyr (4.5%), and alpha-aminobutyric acid (7.6%), and for the intermediate concentration of Asp (8.7%). Between-run precision (CV) was < 3.1% for 17 AAs and < 8.0% for 24 of 25 AAs (CV Asp = 12.0%). For retention times, within-run precision was < 0.4% and between-run precision < 1.8%. Excellent relations were found between the results from the Hitachi L-8500A and the widely used Beckman 6300 analyzer (0.929 < or = r < or = 0.999). The detection was still linear at 5 mumol/L except for Pro and hydroxyproline (20 mumol/L). The upper limit was at least 2500 mumol/L for 13 AAs and at least 1000 mumol/L for 27 of 29 AAs (anserine = 500, Val = 600 mumol/L). Values from 100 human plasma samples agreed with previously published data. We conclude that the results obtained with the Hitachi L-8500A are satisfactory when compared with those of other AA analyzers utilizing the same method. Furthermore, the Hitachi L-8500A displays several advantages including programming flexibility, microsample capacity, low noise plotting, ammonia filtering, and manual repacking of the analytical column.