Induction by Luteinizing Hormone of Ovum Maturation and of Steroidogenesis in Isolated Graafian Follicles of the Rat:Role of RNA and Protein Synthesis

Abstract

Graafian follicles explanted from rat ovaries on the morning of proestrus responded to the addition of ovine luteinizing hormone (NIHLH-S15, 5 μg/ml) in vitro with increased progesterone accumulation and the resumption of oocytic meiosis. After 6 hr incubation with LH, progesterone content of both follicles and media, as determined by radioimmunoassay, was 15 times higher than in controls. During this 6-hr period, no stimulation by LH of overall incorporation of ¹⁴C-leucine into protein or ³H-uridine into RNA was observed. However, inhibition of protein synthesis by puromycin (80 μg/ml) or cycloheximide (5 μg/ml), or inhibition of protein and RNA synthesis by actinomycin D (80 μg/ml), suppressed the effect of LH on both progesterone formation and on ovum maturation; selective inhibition of RNA synthesis by a lower concentration of actinomycin D (8 μg/ml) prevented the stimulation of progesterone production by LH, but failed to block ovum maturation. It is inferred that two classes of proteins are involved in the action of LH on the isolated follicle: the first is required for the resumption of meiosis and its synthesis appears to be regulated at the translational level; the second is essential for steroidogenesis and is controlled at the transcriptional level. The cells responsible for the production of these proteins have not been identified. The action of LH on ovum maturation appears to be independent of progesterone synthesis. (Endocrinology93: 1378, 1973)