Research note: changes in the concentration of beta-carotene, alpha-tocopherol and retinol in the bovine corpus luteum during the ovarian cycle.

Causes and possible consequences of the accumulation of beta-carotene during the development of the corpus luteum in cattle are still unknown. Therefore, in a descriptive study a total of 43 corpora lutea from ovaries of non-pregnant cows representing four stages of the ovarian cycle the concentration of beta-carotene, alpha-tocopherol and retinol was determined. Beta-carotene and alpha-tocopherol continuously increased from stage I to stage IV (beta-carotene: 14 +/- 8 vs. 175 +/- 117 microg/g, P < 0.05; alpha-tocopherol: 15 +/- 7 vs. 132 +/- 66, P < 0.001). In contrast, retinol decreased from highest values at stage I (250 +/- 160 ng/g) to lowest (90 +/- 80 ng/g tissue) at stage III (P < 0.05). The results support the concept, that both beta-carotene and alpha-tocopherol accumulation in the corpus luteum secondary to the uptake of lipoprotein-bound cholesterol during steroid synthesis. Lowest retinol levels were observed at highest metabolic activity of the corpus luteum indicating a possible consumption of retinol during stereogenesis. In conclusion assuming an importance of a local conversion of beta-carotene into retinol in the corpus luteum dietary supplementation should be sufficient enough to support such an accumulation of beta-carotene in the corpus luteum as local precursor of retinol.