428 HBV VACCINATION: BOOSTER DOSE

R.Vi~noli~F.Boni~L.Vecchia,G.Filippi,C.Tramaloni,M.Attclini I A.Marchetti.Divisione di Medicina, Laboratoriod'Analisi, 0sp. S.Anna, USL 13, Castelnovo ne' Monti (RE).

After HBV vaccination of the health care personnel of hour Hospital sub jects with antibody titres fallen below protective values (anti-HBs not tectable or < 10 mIU/ml) were given a booster dose. Up today 26 subjects have been treated with H-B-VAX 20~ug i.m. in the arm. Anti-HBs was assayed one month later by 'Ausab EIA', Abbott Laboratories (titres expressed in mIU/ml). 21 persons (80.8%) had antibody titres >lOOmIU/ml (18 > 200mIU/ml) This anamnestic immunoresponse is most likely due to the persistence of immunologic memory and suggests that protection outlasts the presence of detectable anti-HBs (probably in case of modest antigenic titre).

251 21

1 8

8 2 3

i ~ - , ~ i ~ I , REC~ <18 18-188 >188

HBsAb (mlU/m])

429 EVALUATION OF LIVER FUNCTION BY AN ENDOGENOUS PRODUCT - EXEMPLI- FIED BY UREA SYNTHESIS H. Vilstrup, B. A. Hansen & T. P. Almdal Division of Hepatology, Rigshospitalet, Copenhagen

The synthesis of urea fulfills several demands to a function that may be used for thls purpose: it occurs only in the liver, it is necessary for life and health, and its rate can be measured. However, it has no single sub- strate and its rate varies with both endo- and exogenous factors. The urea- N synthesis rate (UNSR) can most reasonably be related to the blood free amlno-N pool, through which all amino-N for protein synthesis and e.g. glu- coneogenesis must pass. During exogenous stimulation with amino acids UNSR rises linearly in man so that Vmax can not be measured directly. The slope of the relation, having the dimension of a clearance - the Functional Hepa- tic N Clearance (FHNC) - is taken to reflect Vmax. Evidently, most of the essential amino acids do not partake in urea synthesis. In pigs, the process can be saturated. There seems to exist one small and constant UNSR and one larger that depends hyperbolically on the amino acid concentration. In rats, the process is desribable by a substrate inhibition kinetics so that Vmax is never reached, and the capacity of urea-N synthesis (CUNS) can be assessed by the zenith of the relationship. FHNC and CUNS correlate closely with e- stablished liver function measures and in rats with the liver weight after partial hepatectomy. The measures can be used to quantitate metabolic ef- fects of hormones, stress, and chronic disease. The considerations as to standardization of urea synthesis may be extended to apply to endogenous products with even more complicated metabolic relationships.

$220