APOLIPOPROTEIN AI LEVELS ARE INCREASED IN PART AS A CONSEQUENCE OF REDUCED CATABOLISM IN NEPHROTIC RATS

Apolipoprotein AI (ape AI) synthesis, measured as the turnover of I-12 5-labeled apo AI-labeled high-density lipoprotein (HDL), was increased significantly in rats with Heymann nephritis (HN) vs. control Sprague -Dawley (SD) rats. However, fractional apo AI catabolic rate was also significantly less in HN vs. SD. We used I-125-apo AI tyramine cellobi ose HDL, a marker retained at the catabolic site, to establish where a po AI catabolism decreased in six HN rats, seven rats with adriamycin (Adria)-induced nephrosis, and six control SD. Total renal apo AI cata bolism, plus urinary losses, were the same in all three groups, despit e significant urinary apo AI in HN and Adria rats. Apo AT catabolism w as reduced in skin in both nephrotic groups, accounting for similar to 44% of reduced in apo AI catabolism. Thus a significant fraction of a po AI is catabolized in skin of normal male rats. Reduced apo Al catab olism in skin contributes to increased plasma levels in nephrotic rats .