Steady-state concentrations of messenger ribonucleic acid encoding cytochrome P450 side-chain cleavage and 3β-hydroxysteroid dehydrogenase/Δ5,Δ4 isomerase in ovine corpora luteal during the estrous cycle

Abstract

The objective of these experiments was to determine the pattern of mRNA expression for cytochrome P450 side-chain cleavage (P450(scc)) and 3β- hydroxysteroid dehydrogenase/Δ5,Δ4 isomerase (3β-HSD) during luteinization of the follicle and in ovine luteal tissue on Days 3, 6, 9, 12, and 15 of the estrous cycle. Mean concentration of mRNA for P450(scc) was not different in follicles collected 4 or 24 h after the onset of estrus but increased (p < 0.05) 3-fold by 48 h (corpus hemorrhagicum). With the methods used, mRNA for 3β-HSD was not detected until after ovulation and formation of the corpus hemorrhagicum (48 h after onset of estrus). In luteal tissue, mean concentration of mRNA for P450(scc) increased from Days 3 to 9 (p < 0.05) and had decreased (p < 0.05) by Day 15. Mean concentration of mRNA for P450(scc) was higher (p < 0.05) in small luteal cells on Day 9 than on Day 15, with values on Days 6 and 12 being intermediate. In large luteal cells, mean concentrations of P450(scc) mRNA increased (p < 0.05) between Days 6 and 12 and then decreased (p < 0.05) on Day 15. Mean concentration of mRNA for 3β-HSD was not different (p = 0.33) in luteal tissue on any day examined. In small luteal cells, mean concentrations of mRNA for 3β-HSD decreased between Days 6 and 15 (p < 0.05) while in large luteal cells, mean concentrations decreased (p < 0.05) between Days 12 and 15. In summary, up-regulation of mRNA for P450(scc) and 3β-HSD occurred after ovulation. In the CL, concentrations of mRNA for P450(scc) increased from Days 3 to 9 and then decreased again by Day 15. In contrast, concentrations of mRNA for 3β-HSD did not change during the estrous cycle. Large luteal cells had higher concentrations of mRNA for P450(scc) and 3β-HSD than small luteal cells on most days of the estrous cycle examined in this experiment.