Effect of cyclodextrin-encapsulated beta-carotene on progesterone production by bovine luteal cells

Experiments were conducted to examine the effect of cyclodextrin-encapsulat ed beta -carotene on basal or cholesterol (cyclodextrin-encapsulated), LH a nd dibutyryl cyclic AMP (dbcAMP)stimulated progesterone production by bovin e corpus luteum cells isolated from mid-luteal heifer ovaries by collagenas e digestion. Cells were cultured with serum-free DMEM/Ham's F12 medium in s erum pre-treated plastic culture dishes for periods of up to 11 days. Mediu m was replaced after 24h and thereafter every 48h. beta -carotene was added to cultures in a carrier molecule, dimethyl-beta -cyclodextrin, to facilit ate dissolution. All treatments were started on day 3 of culture. Treatment of cells with 1 or 2 mu mol/l beta -carotene resulted in sharp inhibition of progesterone production. On the contrary, treatment of cells with 0.1 mu mol/l beta -carotene resulted in significant stimulation (P < 0.05) of bot h basal and cholesterol-stimulated progesterone secretion. The effect of <b eta>-carotene on LH or dbcAMP-stimulated progesterone production was also e xamined. Treatment of cells with LH or dbcAMP always resulted in stimulatio n of progesterone secretion (P < 0.001). However, cells treated with LH plu s <beta>-carotene or dbcAMP plus beta -carotene both produced significantly (P < 0.01) less progesterone relative to those cells treated with LH or db cAMP alone on days 7, 9 and 11 of culture. These results indicate that <bet a>-carotene can enhance luteal steroidogenesis when present at low concentr ations but is inhibitory at higher concentrations and that encapsulation of beta -carotene in cyclodextrin is an effective method of supplying it to c ells in culture. (C) 2000 Elsevier Science B.V. All rights reserved.