The influence of maternal protein deficiency on the placental transfer of salicylate in rats.

1 The influence of a low protein diet (5% as compared with a control 21% protein diet) on the placental transfer of sodium salicylate was investigated in Sprague-Dawley rats on day 20 of gestation. 2 Maternal plasma salicylate concentrations (assayed by high pressure liquid chromatography) were generally lower in protein-deficient than in control animals at a wide range of times (0.25 - 12 h) and dose levels (2 - 250 mg/kg, i.v.); however, foetal plasma salicylate levels in the two groups of animals did not differ. 3 The placental transfer of salicylate as indicated by the ratio of foetal plasma or foetal liver to maternal plasma salicylic acid concentration was consistently and significantly greater in the protein-deficient group than in the control group of animals following the administration of the drug to the mother as well as to the foetus. 4 A decrease in calorie without a concomitant decrease in protein intake (pair-fed controls) did not alter the placental transfer of salicylate. 5 The increased placental transfer of salicylate in protein-deficient animals could not be attributed to changes in serum protein-salicylate binding. 6 It is suggested that the pharmacokinetic factors responsible for maintaining a lower level of salicylate in the foetus than in the mother are impaired by maternal malnutrition, and this may increase the foetal effects of maternally ingested salicylate.