High dietary protein intake directly stimulates albumin synthesis and albuminuria in rats with Heymann nephritis. Increased albumin synthetic rate might be due to the presence of increased amino acids available for protein synthesis causing more efficient translation of preformed albumin mRNA, or instead might be linked to increased steady state albumin mRNA levels in the liver. Albumin synthesis, hepatic albumin mRNA content, and albumin mRNA relative to β actin mRNA (as an internal control) (Alb/βAct), were measured in rats with Heymann nephritis fed either 8.5% protein (LP), or after protein intake was increased to 40% for 4 days (HP). Enalapril (E) was used to modulate the proteinuric effect of HP, yielding four experimental groups, LPN (8.5% protein nephrotic, no enalapril), LPE (8.5% protein, enalapril treated), HPN (40% protein nephrotic, no enalapril), and HPE (40% protein, enalapril treated). Dietary protein augmentation increased the rate of albumin synthesis, steady-state albumin mRNA levels, and Alb/βAct in both HPN and HPE, compared to either LPN or LPE, even though serum albumin concentration was greater in HPE than in either of the groups fed LP. Both albumin mRNA and Alb/βAct correlated with the rate of albumin synthesis (r = 0.531, P < 0.05; and 0.553, P < 0.01 respectively). Nuclear run-on assays were performed using nuclei isolated from the livers of LPN or HPN to determine whether increased albumin mRNA resulted from an increase in the rate of albumin mRNA transcription. The rate of transcription of albumin mRNA relative to that of 28s ribosomal RNA was 0.071 + 0.007 in LPN versus 0.201 + 0.025 in HPN (P < 0.01) in isolated hepatic nuclei. High protein diets directly stimulates albumin synthesis in nephrotic rats at the level of albumin mRNA transcription.
|Original language||English (US)|
|Issue number||SUPPL. 27|
|State||Published - 1989|
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