Thyroid hormones stimulate oxygen consumption and heat production, inducing the synthesis of reactive oxygen species, which in turn trigger several pathologies including mastitis, and infectious diseases in the newborn calf. The retinol and tocopherol seasonal levels were measured by HPLC in the milk of buffalo cows (winter: 1.60 and 1.20 ?g/ml respectively; summer: 0.71 and 0.76 respectively). In the plasma, seasonal changes for the levels of both antioxidants were not found. The retinol levels in the milk were positively correlated with the plasma levels of T3 (P<0.05), thus suggesting hormone-dependent retinol accumulation. This hypothesis was supported by the finding of increased levels of retinol in the milk (29 or 65%) of cows injected with T3 (2.2 or 4.0 ?g/Kg respectively). The cytosol fraction, extracted from alveolar epithelial cells of mammary glands was incubated with 3H- retinol and, after gel filtration chromatography, one radioactive protein fraction (Mr = 30000) was detected. The amount of labelled proteins was 126% higher in winter (T3 = 1.53 ng/ml) than in summer (T3 = 0.84 ng/ml). We suggest that, in winter, both liposoluble antioxidants are more efficiently transported through the blood-mammary barrier, and that T3 might enhance the retinol uptake by the mammary gland.
Thyroid hormone levels are correlated with the tocopherol and retinol transport in the milk.
Spagnuolo M S;Sarubbi F;Polimeno F;
2003
Abstract
Thyroid hormones stimulate oxygen consumption and heat production, inducing the synthesis of reactive oxygen species, which in turn trigger several pathologies including mastitis, and infectious diseases in the newborn calf. The retinol and tocopherol seasonal levels were measured by HPLC in the milk of buffalo cows (winter: 1.60 and 1.20 ?g/ml respectively; summer: 0.71 and 0.76 respectively). In the plasma, seasonal changes for the levels of both antioxidants were not found. The retinol levels in the milk were positively correlated with the plasma levels of T3 (P<0.05), thus suggesting hormone-dependent retinol accumulation. This hypothesis was supported by the finding of increased levels of retinol in the milk (29 or 65%) of cows injected with T3 (2.2 or 4.0 ?g/Kg respectively). The cytosol fraction, extracted from alveolar epithelial cells of mammary glands was incubated with 3H- retinol and, after gel filtration chromatography, one radioactive protein fraction (Mr = 30000) was detected. The amount of labelled proteins was 126% higher in winter (T3 = 1.53 ng/ml) than in summer (T3 = 0.84 ng/ml). We suggest that, in winter, both liposoluble antioxidants are more efficiently transported through the blood-mammary barrier, and that T3 might enhance the retinol uptake by the mammary gland.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.