Effects of beta-carotene and vitamin A on bovine luteal function

Initially, the direct effects of B-carotene and vitamin A on progesterone (P4) production were studied by exposing dispersed luteal cells to these compounds in vitro. There were no positive relationships between P4 and B-carotene or vitamin A. However, a negative, and perhaps toxic, effect of a large dose of B-carotene on P4 reproduction was noted. A positive relationship between plasma B-carotene and percent change of P4 in the medium of dispersed luteal cells was demonstrated when these plasma metabolites were measured in slaughterhouse cows from which CL were obtained for incubation. This relationship was only present during the winter when plasma levels of B-carotene and vitamin A were considerably lower. Preliminary investigations into the mechanism of action of B-carotene and/or vitamin A were initiated. Luteal tissue ribonucleic acid (RNA), deoxyribonucleic acid (DNA), the RNA to DNA ratio and total protein concentration were measured to study the influence of plasma levels of B-carotene and vitamin A on the protein synthetic capacity of luteal tissue. There were no relationships detected, however, RNA concentration and the RNA to DNA ratio of luteal tissue were greater during the summer. The percent binding of radiolabeled vitamin A was greater in the nuclear than in the cytoplasmic component of the luteal cell