A rapid method for determination of hepatic amino nitrogen to urea nitrogen conversion ('the Functional Hepatic Nitrogen Clearance').
The Functional Hepatic Nitrogen Clearance (FHNC) is a measure of the functional liver mass as to conversion of amino-N to urea-N. FHNC is the slope of the linear regression of multiple samples (10-20) of urea-N synthesis rates (UNSR) on blood alpha-amino-N concentrations (alpha-AN) during infusion of amino acids. UNSR is measured as urinary urea-N excretion rate corrected for accumulation in total body water (TBW) and loss in gut. A simplified method which estimates FHNC from only two samples of UNSR and alpha-AN was developed. Urine was collected in two hourly intervals: before infusion of alanine, and from 2 to 3 h after start of alanine infusion. Blood-urea-N and alpha-amino-N was measured at the beginning and at the end of each urine sampling interval. TBW was estimated from a nomogram, and gut loss of urea was assigned a fixed value (14%). The two-sample FHNC was calculated as delta UNSR (mmol h-1)/delta mean alpha-AN (mmol l-1). Linear regression analysis of the two-sample estimates of FHNC on the 'true' multiple-sample values of FHNC in an independent population of control and cirrhotic subjects showed the two-sample estimates to be closely related with values of the multiple-sample method, the regression equation being: two-sample FHNC = -0.24 + 0.99 x multiple-sample FHNC, r2 = 0.98. A close relationship was also obtained when cirrhotic patients were considered alone: two-sample FHNC = 0.01 + 0.94 x multiple-sample FHNC, r2 = 0.98.(ABSTRACT TRUNCATED AT 250 WORDS)
Hamberg
O
O
Medical Department A, Rigshospitalet, Copenhagen, Denmark.
Vilstrup
H
H
D000588:Amines / Q000493:pharmacokinetics*; D006801:Humans; D016014:Linear Models; D008103:Liver Cirrhosis / Q000378:metabolism; D008657:Metabolic Clearance Rate; D009584:Nitrogen / Q000493:pharmacokinetics*; D012016:Reference Values; D015203:Reproducibility of Results; D013997:Time Factors; D014508:Urea / Q000378:metabolism*
D000588:Amines; D014508:Urea; D009584:Nitrogen