Increased rat mammary tissue vitamin A associated with increased vitamin Aintake during lactation is maintained after lactation

Although increases in dietary vitamin A increase milk vitamin A, little is known about effects of vitamin A intake on mammary tissue vitamin A levels during and after the reproductive cycle. First, we measured vitamin A conce ntrations in milk, mammary tissue and liver of lactating rats fed 0, 4, or 50 mu mol of vitamin A/kg diet during pregnancy and through d 12 of lactati on. Liver vitamin A concentration was significantly affected by diet in lac tating females and pups 12 d after parturition, Milk vitamin A concentratio ns were significantly higher (7.1 +/- 2.2 mu mol/L, n = 8) in dams fed 50 m u mol/kg than in those fed 0 or 4 mu mol/kg (1.9 +/- 0.3, n = 5 and 2.9 +/- 0.7 mu mol/L, n = 7; P < 0.001), as were mammary tissue vitamin A concentr ations (5.1 +/- 1.1 versus 2.2 +/- 0.4 and 2.4 +/- 0.6 nmol/g; P < 0.001). Next, we maintained female rats on 50 or 10 mu mol vitamin A/kg diet during pregnancy and lactation and then on 4 mu mol/kg diet after pups were weane d on d 21. On d 21, mammary tissue vitamin A concentrations were 3.14 +/- 0 .75 versus 1.52 +/- 091 nmol/g in dams fed 50 versus 10 mu mol/kg (n = 4/gr oup; P < 0.001), Mammary tissue vitamin A concentrations were not significa ntly affected by time from 7 to 49 d after lactation and averaged 8.5 +/- 0 .4 and 4.9 +/- 0.8 nmol/g on d 49 in dams fed 50 versus 10 mu mol/kg (n = 4 ; p < 0.001), We conclude that diet-induced differences in rat mammary tiss ue vitamin A developed during pregnancy and lactation are maintained for gr eater than or equal to7 wk after lactation.