title: 26-cholesterol hydroxylase in rat corpora lutea: A negative regulator of progesterone secretion.
abstract: From a subtracted cDNA library of rat luteal tissue, where cDNA fragments in functional luteal tissue were subtracted from those in regressing luteal tissue, a cDNA clone corresponding to 26-cholesterol hydroxylase (P450(C26)) was obtained. It is known that P450(C26) catalyzes the conversion of cholesterol to 26-hydroxycholesterol, which blocks cholesterol utilization in the cell, and that 20alpha-hydroxysteroid dehydrogenase (20alpha-HSD) catalyzes the conversion of progesterone to an inactive steroid, 20alpha-dihydroprogesterone (20alpha-OHP). Thus, using pseudopregnant rats as a model, physiological cooperation of P450(C26) and 20alpha-HSD in the reduction of progesterone release toward the end of the luteal phase was evaluated. Levels of P450(C26) and 20alpha-HSD mRNA were examined in corpora lutea from pseudopregnant rats by Northern blot or reverse transcription-polymerase chain reaction or both. P450(C26) mRNA was ubiquitously expressed in corpora lutea, and its expression increased toward the end of pseudopregnancy, while 20alpha-HSD was expressed in all corpora lutea on Day 16 (Day 0 = the day of after cervical stimulation) but not detected before Day 10. An inhibitor of 20alpha-HSD, STZ26 (D-homo-16-oxa-4-androstene-3,16alpha-dione), was administered at various doses to rats from Day 12 to 20, effectively suppressing the elevation of 20alpha-OHP in a dose-dependent manner but not the depletion of progesterone completely. The expression of P450(C26) mRNA was increased as STZ26 dose increased, which negatively correlated with the progesterone levels. These results strongly suggest that P450(C26) cooperated with 20alpha-HSD in the reduction of progesterone release from the rat luteal tissue at the end of the functional luteal phase.
authors.affiliation: Department of Veterinary Physiology, Veterinary Medical Science, The University of Tokyo, Tokyo 113, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Yoshida
authors.forename: K
authors.initials: K
authors.lastname: Kubota
authors.forename: H
authors.initials: H
authors.lastname: Sasaki
authors.forename: T
authors.initials: T
authors.lastname: Hasegawa
authors.forename: M
authors.initials: M
authors.lastname: Nishihara
authors.forename: M
authors.initials: M
authors.lastname: Terada
authors.forename: M
authors.initials: M
authors.lastname: Takahashi
mesh_terms: D015089:20-Hydroxysteroid Dehydrogenases / Q000037:antagonists & inhibitors / Q000235:genetics; D043607:20-alpha-Hydroxysteroid Dehydrogenase; D000735:Androstenedione / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D015152:Blotting, Northern; D053493:Cholestanetriol 26-Monooxygenase; D003338:Corpus Luteum / Q000201:enzymology*; D018076:DNA, Complementary / Q000302:isolation & purification; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D015870:Gene Expression; D008183:Luteal Phase; D010053:Ovary / Q000187:drug effects / Q000201:enzymology; D011374:Progesterone / Q000378:metabolism*; D011555:Pseudopregnancy; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017208:Rats, Wistar; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013250:Steroid Hydroxylases / Q000235:genetics / Q000378:metabolism*
chemical_list: C110171:D-homo-16-oxa-4-androstene-3,16alpha-dione; D018076:DNA, Complementary; D004791:Enzyme Inhibitors; D012333:RNA, Messenger; D000735:Androstenedione; D011374:Progesterone; D015089:20-Hydroxysteroid Dehydrogenases; D043607:20-alpha-Hydroxysteroid Dehydrogenase; D013250:Steroid Hydroxylases; D053493:Cholestanetriol 26-Monooxygenase