A comparative study between responses of isolated bovine and equine digital arteries to vasoactive mediators

Melatonin improves the maturation and developmental ability of bovine oocytes by up-regulating GJA4 to enhance gap junction intercellular communication

Melatonin (MT) increases oocyte maturation by reducing reactive oxygen species level and enhancing oocyte antioxidant capacity. However, the mechanisms via which MT works are still poorly understood. In the present study, the effects of MT on the maturation rate and development ability of bovine oocytes were investigated. Then, the transcriptome of oocytes treated by MT was sequenced. Finally, the expression of gap junction protein alpha 4 (GJA4) protein and cAMP level were detected in bovine oocytes, and isoprenaline (enhancer of gap junctional intercellular communication (GJIC)) and heptanol (inhibitor of GJIC) were used to investigate the effect of MT on GJIC activity in bovine oocytes. Our results showed that MT significantly improved the maturation, developmental ability and mRNA expression of GJA4 of bovine oocytes. Meanwhile, MT significantly increased GJA4 protein level and cAMP level in bovine oocytes. In contrast to heptanol, both isoproterenol and MT significantly increased GJIC activity, nuclear maturation and the development ability of bovine oocytes. However, MT significantly restored the nuclear maturation and developmental ability of oocytes treated by heptanol. In conclusion, our results showed that MT improves the maturation and developmental ability of bovine oocytes by enhancing GJIC activity via up-regulating GJA4 protein expression in IVM progress.

Endothelium-dependent relaxation mechanisms involve nitric oxide and prostanoids in the isolated bovine digital vein

Endothelial dysfunction contributes to the development of ungulate's laminitis. Although extensively studied in equines, the endothelial function is not fully examined in bovine digital veins (BDVs). BDVs were studied under isometric conditions to describe the acetylcholine (ACh) endothelium-dependent relaxation. Concentration-response curves were constructed to phenylephrine, ACh, and sodium nitroprusside (SNP). Relaxation responses were evaluated using either phenylephrine or depolarizing high-potassium Krebs solution (DKS) as precontraction agents. Endothelium denudation and incubation with L-NAME (300 μM), indomethacin (10 μM) or both were used to explore endothelial-mediated mechanisms. Endothelium denudation did not modify phenylephrine and SNP responses, however, significantly (p < 0.05) converted a relaxation (63.2 ± 5%) response to ACh into a contraction (30.3±9%). The ACh-evoked relaxation was significantly (p < 0.05) reduced in the presence of indomethacin (37.5 ± 6%) and L-NAME (6.40 ± 2%). The presence of both inhibitors abolished the ACh-evoked relaxation. Although DKS caused a higher precontraction than phenylephrine, ACh-evoked relaxation (22.4 ± 3.4%) was still observed and was reduced by the combination of inhibitors (7.0 ± 1.0%). The ACh endothelium-dependent relaxation in BDVs is essentially mediated by nitric oxide and endothelium-derived prostanoids. The BDV endothelium function is a dynamic component in the control of the bovine digital blood flow, particularly under endothelial dysfunction conditions when venoconstriction might lead to postcapillary resistance increase.