Malaria infection impairs glucuronidation and biliary excretion by the isolated perfused rat liver

Abstract

1. The effect of the erythrocytic stage of malaria infection on hepatic glucuronidation, biliary excretion and oxidation processes was investigated using harmol, salbutamol, taurocholate and propranolol. Livers from rats infected with the rodent malaria parasite P. berghei were isolated and perfused in a single-pass (harmol, taurocholate, propranolol) or recirculating (harmol, salbutamol) design. The degree of erythrocytic parasitaemia ranged from 16% to 63%.

2. The hepatic clearance (Cl) of harmol decreased from 7˙8±0˙4 ml/min in controls to 5˙7±1˙1 ml/min in the malaria-infected group in single-pass studies. This corresponded to a 40–60% reduction in hepatic intrinsic clearance (Cl_int). Similar changes were observed using the recirculating design when glucuronidation accounted for >90% of harmol metabolism.

3. The Cl of salbutamol, metabolized exclusively by glucuronidation under the conditions used, also decreased significantly from 8˙5±0˙8 in controls to 6˙6±1˙4 ml/min in the malaria-infected group. This corresponded to a 40–70% reduction in Cl_int.

4. The Cl of taurocholate, excreted unchanged in bile, decreased slightly but significantly from 9˙6±0˙3 ml/min in controls to 8˙3±0˙9 ml/min in the malaria-infected group. In the same livers, there was also a slight but significant decrease in propranolol Cl (10˙0±0˙1 ml/min and 9˙9±0˙1 ml/min, respectively). Both these compounds undergo flow-limited hepatic clearance; the decreases in Cl_int of taurocholate and propranolol were 87% and 35%, respectively.

5. Cl and Cl_int of each of the compounds studied were found to correlate significantly with the degree of erythrocytic parasitaemia. This study shows that glucuronidation, biliary excretion and oxidation by liver are impaired in malaria infection in rats, with biliary excretion being the most affected. The data indicate that there is a general decrease in hepatic elimination processes during the erythrocytic phase of malaria infection.