Effects of N-carbamylglutamate and L-arginine on steroidogenesis and gene expression in bovine granulosa cells

Feeding N-carbamylglutamate (NCG) and arginine (ARG) improves reproductive measures in pigs and reduces systemic steroid levels in pregnant ewes. We hypothesized that the effects of NCG and ARG on reproduction were due to direct effects on the ovary. Thus, the objectives of this study were to investigate the effects of NCG and ARG on granulosa cell (GC) steroidogenesis, gene expression, and cell proliferation in vitro. GC were collected from small (1-5 mm) bovine follicles and treated in vitro with NCG or ARG in serum-free medium for 24 h to 48 h. Both NCG and ARG inhibited (P < 0.05) IGF1- and FSH-induced GC estradiol production but only NCG inhibited (P < 0.05) progesterone production. In contrast, NCG and ARG increased (P < 0.05) GC numbers induced by IGF1 and FSH. NCG inhibited (P < 0.05) StAR, CYP11A1 and CYP19A1 mRNA abundance in small-follicle GC, whereas ARG had no effect (P > 0.10) on StAR, CYP11A1 or CYP19A1 mRNA abundance. We conclude that NCG and ARG may act directly on GC and therefore may regulate ovarian function by slowing follicular differentiation via inhibiting IGF1 action, and steroid synthesis while stimulating GC proliferation in cattle.