THE SIGNIFICANCE OF CAROTENES AND OF VITAMIN-A FOR THE REPRODUCTION OF CATTLE, OF HORSES AND OF PIGS - A REVIEW

The carotenes are transported by lipoproteins into the cells of the te rtiary follicles and corpora lutea and have an effect as antioxidants, as activators of progesterone-synthesis and as provitamins A. There e xist a high activity of carotinase in the tertiary follicles and in co rpora lutea. Vitamin A is oxidized to 9-cis- and all-trans-retinoic ac id, which are bound to receptors and stimulate the transcription from many genes: they promote the synthesis of proteins, of estrogens and o f progesterone. The effect of a supplementation of p-carotene on the r eproduction of cows, mares and sows is described. Retinoid acid is nec essary for the function of the germ epithel, of Sertoli-cells and of i nterstitial cells.