Fluctuations in rat liver alanine-amino-transferase activity during experimental nippostrongylosis

Abstract

SUMMARYThe activity of the gluconeogenic enzyme, alanine-amino-transferase (ALT), in a preparation from the liver of rats was studied by means of anin vitroassay throughout the course of a primary infection ofNippostrongylus brasiliensis, established by a subcutaneous injection of approximately 4000 3rd-stage larvae. The activity was measured on days 1–14 p.i. in both uninfected and infected rats and a marked pattern in the enzyme's activity was observed. In infected rats, the activity increased from 1·46±0·19 U/g liver on day 1 p.i. to a peak on day 4 p.i. of 10·75±1·62 U/g liver, then decreased to a trough of 0·44±0·18 U/g liver on day 10 p.i. before returning to original levels by day 14 p.i., by which time the infection had been largely eliminated. In uninfected rats the activity of the liver enzyme remained constant throughout this period with a value of 2·54±0·12 U/g liver. The activity of the enzymein vitrowas found to be related to the size of the inoculum on days 4 and 10 p.i. It was proposed that these observations could be due to either (1) a direct effect of the parasite, or (2) a consequence of the host immune response to the infection. In order to investigate the second proposition more fully, liver ALT activity was investigated byin vitroassay on selected days p.i. in rats experiencing a secondaryN. brasiliensisinfection. In these rats the liver ALT activity was observed to reach a peak on day 2 p.i., with an activity of 3·87 ± 0-28 U/g liver, and a trough on day 4 p.i. with an activity of 0·11 ±0·03 U/g liver, returning to similar levels to those measured in uninfected rats by day 7 p.i. When serum prepared from rats having secondaryN. brasiliensisinfections collected on day 4 p.i. was added to the assay, a reduction in the activity of liver ALT activity from both the infected and uninfected rats was measured byin vitroassay. The results are discussed in relation to protein metabolism and gluconeogenesis in rats infected withN. brasiliensis, and also in relation to the host’s immune response to the parasitic infection.