Adrenocortical sensitivity to ACTH in neonatal rats: correlation of corticosterone responses and adrenal cAMP content

A coordinated hypothalamic-pituitary-adrenal axis response is important for the survival of newborns during stress. We have previously shown that prior to post-natal day (PD) 5, neonatal rats exposed to hypoxia (one of the most common stressors effecting premature neonates) exhibit a large corticosterone response without a drastic increase in immunoassayable plasma ACTH and without a detectable increase in adrenal cAMP content (the critical second messenger). To explore this phenomenon and to further our knowledge of the mechanism of steroidogenesis in the neonate, we investigated the adrenal response to exogenous ACTH in the normoxic neonatal rat. Rat pups at PD2 and PD8 were injected (IP) with porcine ACTH at a low, moderate, or high doses (1, 4, or 20 µg/kg body weight). Trunk blood and whole adrenal glands were collected at baseline (before injection) and 15, 30, or 60 minutes after the injection. ACTH stimulated corticosterone release in PD2 and PD8 pups. In PD2 pups, plasma corticosterone at baseline and during the response to ACTH injection was greater than values measured in PD8 pups, despite lower adrenal cAMP content in PD2 pups. Specifically, the low and moderate physiological ACTH doses produced a large corticosterone response in PD2 pups without a change in adrenal cAMP content. At extremely high, pharmacological levels of plasma ACTH in PD2 pups (exceeding 3000 pg/mL), an increase in adrenal cAMP was measured. We conclude that physiological increases in plasma ACTH may stimulate adrenal steroidogenesis in PD2 pups through a non-cAMP mediated pathway

Detection methods and their limitations: PSP toxins in the southern puffer fish Sphoeroides nephelus responsible for human poisoning events in Florida in 2004

High-performance liquid chromatography (HPLC) with post-column derivatisation and fluorescence detection has been commonly used for analysing paralytic shellfish poisoning (PSP) toxins. However, identifyingpeaks with confidence requires that steps be taken beyond simple chromatographic runs, owing in part to the abundance of substances in natural samples that have intrinsic fluorescence and may co-elute with toxins. The aim of this study was to assess HPLC toxin detectionin samples collected from two puffer fish poisoning (PFP) events. Since 2002, PSP toxins have been detected in southern puffer fish Sphoeroides nephelus from the Titusville region of Florida. Despite a current harvestingban on southern puffer fish in this area, PFP reports continue. Unconsumed puffer fish from two human poisoning events in 2004 were analysed by HPLC for PSP toxins. Saxitoxin was the dominant congener inunconsumed puffers. Decarbamoyl saxitoxin and B1 were also detected. These toxins were confirmed through a series of HPLC steps and subsequently by other methods. This work serves as an example ofprocedures necessary for HPLC toxin detection, provides a comparison of HPLC with other detection methods, and demonstrates the continued threat of PSP toxicity associated with puffer fish from the Titusville area ofFlorida

Adrenocortical sensitivity to ACTH in neonatal rats: correlation of corticosterone responses and adrenal cAMP content

A coordinated hypothalamic-pituitary-adrenal axis response is important for the survival of newborns during stress. We have previously shown that prior to post-natal day (PD) 5, neonatal rats exposed to hypoxia (one of the most common stressors effecting premature neonates) exhibit a large corticosterone response without a drastic increase in immunoassayable plasma ACTH and without a detectable increase in adrenal cAMP content (the critical second messenger). To explore this phenomenon and to further our knowledge of the mechanism of steroidogenesis in the neonate, we investigated the adrenal response to exogenous ACTH in the normoxic neonatal rat. Rat pups at PD2 and PD8 were injected (IP) with porcine ACTH at a low, moderate, or high doses (1, 4, or 20 µg/kg body weight). Trunk blood and whole adrenal glands were collected at baseline (before injection) and 15, 30, or 60 minutes after the injection. ACTH stimulated corticosterone release in PD2 and PD8 pups. In PD2 pups, plasma corticosterone at baseline and during the response to ACTH injection was greater than values measured in PD8 pups, despite lower adrenal cAMP content in PD2 pups. Specifically, the low and moderate physiological ACTH doses produced a large corticosterone response in PD2 pups without a change in adrenal cAMP content. At extremely high, pharmacological levels of plasma ACTH in PD2 pups (exceeding 3000 pg/mL), an increase in adrenal cAMP was measured. We conclude that physiological increases in plasma ACTH may stimulate adrenal steroidogenesis in PD2 pups through a non-cAMP mediated pathway