1. A pharmacokinetic study of valnemulin was conducted in healthy Muscovy ducks after intravenous (IV), intramuscular (IM) and oral administrations at a dose rate of 15 mg/kg body weight. 2. Drug concentrations in plasma were determined by high performance liquid chromatography-tandem mass spectrometry (LC-MS/MS). Pharmacokinetics parameters of valnemulin were analysed by compartmental analysis using the WinNonlin program. 3. After IV administration, valnemulin was widely distributed with a volume of distribution based on a terminal phase (V(z)) of 8·19 ± 3·07 l/kg, a mean elimination half-life (t(1/2Ke)) of 2·63 h, and a clearance (Cl) value of 5·56 ± 1·53 l/kg/h. Following intramuscular and oral administration, valnemulin was rapidly absorbed; the C(max) was 0·44 ± 0·13 and 0·12 ± 0·02 µg/ml (achieved at 0·28 and 1·80 h), the t(1/2Ke) was 3·17 ± 3·83 and 4·83 ± 1·81 h, and the absolute bioavailability (F) was 72% and 37%, respectively. 4. The plasma profile of valnemulin exhibited favourable pharmacokinetic characteristics in Muscovy ducks, such as wide distribution, and rapid absorption and elimination, though oral bioavailability was low.

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Nitrogen (N) and phosphorus (P) are two primary components of fertilizers for crop production. Coordinated acquisition and utilization of N and P are crucial for plants to achieve nutrient balance and optimal growth in a changing rhizospheric nutrient environment. However, little is known about how N and P signaling pathways are integrated. We performed transcriptomic analyses and physiological experiments to explore gene expression profiles and physiological homeostasis in the response of rice (Oryza sativa) to N and P deficiency. We revealed that N and P shortage inhibit rice growth and uptake of other nutrients. Gene Ontology (GO) analysis of differentially expressed genes (DEGs) suggested that N and Pi deficiency stimulate specific different physiological reactions and also some same physiological processes in rice. We established the transcriptional regulatory network between N and P signaling pathways based on all DEGs. We determined that the transcript levels of 763 core genes changed under both N or P starvation conditions. Among these core genes, we focused on the transcription factor gene NITRATE-INDUCIBLE, GARP-TYPE TRANSCRIPTIONAL REPRESSOR 1 (NIGT1) and show that its encoded protein is a positive regulator of P homeostasis and a negative regulator of N acquisition in rice. NIGT1 promoted Pi uptake but inhibited N absorption, induced the expression of Pi responsive genes PT2 and SPX1 and repressed the N responsive genes NLP1 and NRT2.1. These results provide new clues about the mechanisms underlying the interaction between plant N and P starvation responses.

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