ABSTRACT
The biological action of steroids in many plant species appears comparable to that in animals. The cellular effect of such steroids in microbes and plants appears, by and large, to be comparable to that in mammals. The corpus luteum is a unique source of steroids, carotenoids and retinoids in mammals. Retinol is also important for the synthesis of cholesterol and the metabolism of various steroids, such as pregnenolone, progesterone. Ovarian carotenoids were reported in 1913 and again in 1930. The decreased expression of progesterone receptors resulted in impaired responsiveness to progestins, suggesting that retinoids might modulate the effects of steroid hormones in breast cancer and reduce the sensitivity of breast cancers to progestin therapy. Retinol is important for the synthesis of cholesterol and the metabolism of various steroids, such as pregnenolone and progesterone. The biosynthetic pathway for the formation of isoprenoid compounds in plants is based on the pathway of sterol biosynthesis studied for many years in animals and yeast.
