General and comparative endocrinology最新文献

Integrated approaches to physiology and ecology offer powerful tools to assess individual- and population-level health. Although hair glucocorticoid analysis is widely used as a physiological indicator, hair progesterone has recently attracted attention as a potential measure of reproductive health that may integrate information on past reproductive activity. Here, we examined the assay validation and biological utility of hair progesterone analysis as an indicator of long-term reproductive activity in Pallas's squirrel Callosciurus erythraeus. A hair progesterone enzyme immunoassay was validated and used to compare hair progesterone concentrations (HPC) between sexes and age classes. The effects of current and past reproductive activity (pregnancy and number of placental scars), body condition, age, and season (hair non-growth vs. growth season) on adult female HPC were investigated. The analytical assay validation was successful. Adult females had significantly higher HPC than juvenile males, adult males, and juvenile females. Although there was no effect of current reproductive activity, past reproductive activity (as indexed by the number of placental scars) significantly influenced adult female HPC, such that female Pallas's squirrels with more placental scars had higher HPC. There was also a significant positive impact of season on HPC, and females with better body condition tended to have higher HPC. Hair progesterone is therefore an integrative physiological indicator of past reproductive activity in Pallas's squirrels, with potential applications in the prediction of population dynamics to inform the management of this invasive squirrel.

Hagfishes are representatives of the phylogenetically important, early-branching vertebrate lineage Agnatha, and many endocrine signaling systems in this group remain poorly understood. In this study, we provide the first molecular and functional characterization of melanocortin receptors (Mcrs) and their accessory protein (Mrap) in hagfishes. Using genomic and transcriptomic resources from inshore hagfish (Eptatretus burgeri), Pacific hagfish (Eptatretus stoutii), and Atlantic hagfish (Myxine glutinosa), we identified genes encoding two hagfish melanocortin receptors, Mcar and Mcbr, and a single Mrap. When expressed in mammalian cells, both receptors responded to human ACTH(1-24) and α-MSH with similar affinities. Co-expression with Mrap reduced maximal activity of Mcbr but not Mcar and only modestly modulated the ligand sensitivity of either receptor. Gene expression analyses revealed that mcbr and mrap are prominently expressed in the slime gland, a tissue that also transcriptionally expressed the steroidogenic enzymes star and cyp11a1, whereas mcar is most prominently expressed in the brain. These findings suggest that hagfish Mcrs retain broad ligand responsiveness and relative Mrap-independence, consistent with a hypothesized ancestral mode of melanocortin signaling. Although no genes encoding known melanocortin prohormones have yet been identified in hagfish genomes, the presence of functional receptors and tissue-specific expression patterns suggest these genes may have physiological roles and that an as-yet-unidentified ligand may exist in hagfish. Together, these results provide new insight into the organization and evolution of the vertebrate melanocortin system and highlight hagfish as a key model for reconstructing the functional evolution of this essential endocrine signaling pathway.

We developed and validated a fluorescence-based competitive enzyme-linked immunosorbent assay (ELISA) for the parallel quantification of four key pituitary hormones-growth hormone (GH), prolactin (PRL), somatolactin alpha (SLα), and somatolactin beta (SLβ)-in grass carp (Ctenopharyngodon idella). The assay utilizes recombinant grass carp hormones as standards and corresponding rabbit polyclonal antibodies, with biotin-avidin-HRP amplification and HPPA-based fluorescence detection. Standard curves demonstrated high linearity and half-maximal inhibitory concentrations (ID₅₀) ranging from 8.004 to 18.63 ng/mL. We successfully applied this ELISA to quantify hormone levels in plasma and culture medium from primary pituitary cell culture after stimulation with GHRH, SST, cortisol, and CRH, confirming its ability to detect physiologically relevant changes. This reliable, sensitive, and cost-effective ELISA provides a valuable tool for monitoring endocrine status in grass carp, with potential applications in growth performance assessment, reproductive management, and stress response studies in aquaculture. The method may also be adaptable to other cyprinid species due to high hormone sequence conservation.