RT Journal Article
SR Electronic
T1 BRAIN CYCLOSPORIN A LEVELS ARE DETERMINED BY ONTOGENIC REGULATION OF <em>MDR1A</em> EXPRESSION
JF Drug Metabolism and Disposition
JO Drug Metab Dispos
FD American Society for Pharmacology and Experimental Therapeutics
SP 288
OP 295
DO 10.1124/dmd.105.007427
VO 34
IS 2
A1 Kerry B. Goralski
A1 Philip D. Acott
A1 Albert D. Fraser
A1 David Worth
A1 Christopher J. Sinal
YR 2006
UL http://dmd.aspetjournals.org/content/34/2/288.abstract
AB Cyclosporin A (CyA) toxicity is a common occurrence in pediatric organ transplant patients. We hypothesized that reduced mdr1a expression in newborn and developing mice would affect CyA accumulation within organs and/or toxicity. For functional studies, CyA was administered (5 mg kg–1 i.p.) to 1-, 12-, and 19-day, and adult male and female mdr1a+/+ and mdr1a–/– mice. Peak blood CyA was lower in 1-, 12-, and 19-day-old (1000 ng ml–1) versus adult (1500 ng ml–1) mice but was similar in mdr1a+/+ and mdr1a–/– mice. Kidney mdr1a expression (measured by quantitative polymerase chain reaction) increased 2.5-fold in 19-day-old male and female mice and increased another 4-fold in adult females compared with adult males. Liver mdr1a expression increased 6-fold by day 12 compared with neonatal mice. Thereafter, maintenance of hepatic mdr1a expression in females and a reduction to neonatal levels in males was observed. Kidney/blood (8- to 9-fold) and liver/blood (12- to 15-fold) CyA levels were highest on days 12 and 19 and were not dependent on maturational changes in mdr1a mRNA levels. Adults had higher brain expression of mdr1a mRNA (3-fold), a corresponding 5-fold increase in immunodetectable P-glycoprotein, and 80% lower brain accumulation of CyA compared with 1-day-old mice. Conversely, in mdr1a-null mice, brain/blood CyA was similar in newborn and adult mice. A similar pattern was observed for the brain accumulation of the mdr1a substrate 3H-digoxin. We conclude that the risk for central nervous system drug toxicity could be higher in neonates or young children as a consequence of underdeveloped P-glycoprotein. The American Society for Pharmacology and Experimental Therapeutics