The effects of ascorbic acid deficiency and repletion on pulmonary, renal, and hepatic drug metabolism in the guinea pig

Abstract

The effects of ascorbic acid (AA) deficiency on microsomal and soluble (postmicrosomal supernatant) enzymes which catalyze drug metabolism were studied in the guinea pig liver, lung, and kidney, (i) Twenty-one days of AA depletion produced a 50–60% decrease in hepatic cytochrome P-450 levels, 20–30% decreases in renal levels, but no significant changes in pulmonary cytochrome P-450 content. Upon repletion of ascorbic acid, recovery to control levels occurred within 7 days. (ii) The decreases in hepatic cytochrome P-450 in scurvy were not accompanied by a corresponding increase in cytochrome P-420. (iii) Aminopyrine N-demethylation decreased by 40% in livers of deficient animals, and recovered within 3 days, but there were no corresponding changes in lungs and kidneys. (iv) There were no significant alterations of NADPH-cytochrome c reductase activity in scorbutic animals in any of the three organs. (v) Activity of “native” UDP-glucuronyl transferase was increased in liver microsomes after 21 days of deficiency, but this apparent increase was not observed when the enzyme was fully activated in vitro with UDP N-acetylglucosamine. “Native” UDP-glucuronyl transferase was increased in kidneys of deficient animals and unchanged in lungs. (vi) In the postmicrosomal supernatant, glutathione S-aryl transferase activity in deficient livers decreased tc 50% of control and did not fully recover after 14 days of ascorbic acid repletion. These changes were not seen in kidney and lung. (vii) Also in the postmicrosomal supernatant, p-aminobenzoic acid (PABA) N-acetyl transferase activity increased in the kidneys of deficient animals, but was unchanged in liver and lungs. (viii) Addition of ascorbic acid in vitro to hepatic microsomes prepared from scorbutic animals had no effect on activities of aminopyrine N-demethylase, NADPH-cytochrome c reductase, PABA N-acetyl transferase, and glutathione S-aryl transferase.