Studies on the rapid cholesterol-depleting and steroidogenic actions of luteinizing hormone in the rat ovary: effects of aminoglutethimide phosphate

1970 ◽  
Vol 48 (8) ◽  
pp. 881-884 ◽  
Author(s):  
Harold R. Behrman ◽  
David T. Armstrong ◽  
Roy O. Greep
Keyword(s):  
Luteinizing Hormone ◽  
Cholesterol Ester ◽  
Free Cholesterol ◽  
Tissue Concentration ◽  
Control Level ◽  
Side Chain ◽  
Tissue Levels ◽  
Chain Cleavage ◽  
Luteal Tissue ◽  
Rat Ovary

Superovulated, immature rats were administered luteinizing hormone (LH) and/or aminoglutethimide phosphate (AGP), an inhibitor of cholesterol side-chain cleavage, to ascertain whether the steroidogenic action could be separated from the cholesterol-depleting action of LH. The injection of AGP [Formula: see text] and [Formula: see text] before sacrifice significantly reduced tissue levels of progesterone and 20α-dihydroprogesterone to 25–30% of normal, and increased tissue levels of free cholesterol in the absence and presence of LH given [Formula: see text] or 4 h before sacrifice. Cholesterol ester concentration was increased twofold after [Formula: see text] AGP, whereas LH injection [Formula: see text] after AGP and 4 h before sacrifice reduced the tissue concentration to the control level but not as low as that observed when only LH was given 4 h before sacrifice (50% of control level). The cholesterol ester depletion induced by LH, even though steroidogenesis was inhibited, indicates that these may represent separate events in the action of LH on luteal tissue.

scholarly journals The compartmentation of non-esterified and esterified cholesterol in the superovulated rat ovary

1971 ◽  
Vol 123 (2) ◽  
pp. 143-152 ◽  
Author(s):  
A. P. F. Flint ◽  
D. T. Armstrong
Keyword(s):  
Microsomal Fraction ◽  
Specific Radioactivity ◽  
Subcellular Fractions ◽  
Side Chain ◽  
Electron Microscopic ◽  
Side Chain Cleavage ◽  
Chain Cleavage ◽  
Cleavage Enzyme ◽  
Rat Ovary

1. The specific radioactivities of non-esterified and esterified cholesterol, progesterone and 20α-hydroxypregn-4-en-3-one were determined in slices of superovulated rat ovary after incubation with [1-14C]acetate in vitro for various times. The specific radioactivities of progesterone and 20α-hydroxypregn-4-en-3-one were equal, and (during the fourth hour of incubation) exceeded those of the non-esterified cholesterol and the esterified cholesterol by factors of 2.8 and 7.6 respectively. 2. After separation of homogenates of superovulated rat ovary slices previously incubated with [14C]acetate into subcellular fractions by differential centrifugation, the specific radioactivities of non-esterified cholesterol in the cytosol, mitochondria, lipid-containing storage granules and microsomal fraction were 1220, 1510, 1420 and 4020d.p.m./μmol respectively; the corresponding values for the specific radioactivity of the esterified cholesterol were 600, 700, 730 and 760d.p.m./μmol. The specific radioactivities of progesterone and 20α-hydroxypregn-4-en-3-one were equal in all fractions; the corresponding mean specific radioactivity of progesterone+20α-hydroxypregn-4-en-3-one was 6150d.p.m./μmol. 3. By using glutamate dehydrogenase and cytochrome (a+a3) as mitochondrial markers, the presence of cholesterol side-chain cleavage enzyme was demonstrated in microsomal fraction free of mitochondrial contamination. 4. The specific radioactivities of ovarian non-esterified and esterified cholesterol, progesterone and 20α-hydroxypregn-4-en-3-one were determined up to 8h after the intravenous injection of [4-14C]cholesterol into superovulated rats. At all times the specific radioactivities of progesterone and 20α-hydroxypregn-4-en-3-one were equal to the specific radioactivity of non-esterified cholesterol and exceeded, by up to 3.3-fold, that of the esterified cholesterol. 5. It is concluded that non-esterified cholesterol formed from [14C]acetate in the endoplasmic reticulum equilibrates slowly with non-esterified cholesterol in other subcellular fractions, and is preferentially converted into steroids. Such a mechanism presupposes the operation of a microsomal cholesterol side-chain cleavage enzyme using non-esterified cholesterol as its substrate. Unrelated evidence is presented in support of the existence of such an enzyme. The results are discussed in the light of other biochemical and electron-microscopic findings relating to the compartmentation of cholesterol in steroidogenic tissues.

OESTROGEN BIOSYNTHESIS BY THE RAT OVARY IN EARLY PREGNANCY

1972 ◽  
Vol 69 (1) ◽  
pp. 127-140 ◽  
Author(s):  
A. Zmigrod ◽  
H. R. Lindner
Keyword(s):  
Early Pregnancy ◽  
Side Chain ◽  
Interstitial Tissue ◽  
Corpora Lutea ◽  
Microsomal Preparation ◽  
Pregnant Rats ◽  
Side Chain Cleavage ◽  
Chain Cleavage ◽  
Rat Ovary

ABSTRACT Ovarian homogenates or microsomes from pregnant rats were capable of aromatizing C19-steroids (testosterone or androstenedione) in the presence of NADPH to form oestrone and 17β-oestradiol; the microsomal preparation was also capable of forming these oestrogens from progesterone. The rate of oestrogen formation from either type of substrate increased during the first week of pregnancy. Aromatizing activity reached a plateau by about the fifth to sixth day after mating, at a level similar to that found in the ovaries of pro-oestrous rats. Side-chain cleaving activity continued to rise until the seventh day of pregnancy, yet remained far below that in pro-oestrous animals. Hence side-chain cleavage, rather than aromatizing activity, must limit oestrogen formation during early pregnancy. Isolated corpora lutea of pregnancy and the remainder of the ovary, consisting of involuting corpora lutea, small follicles and interstitial tissue, contributed about equally to ovarian oestrogen production from progesterone under the in vitro conditions. Neither aromatizing nor side-chain splitting activity showed a distinct peak on the fourth day of pregnancy, the time of the putative prenidatory oestrogen surge.

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