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Home / Equine Research Bank / J Endocrinol / Effect of insulin-induced hypoglycaemia on secretion pattern...
The Journal of endocrinology1997; 153(3); 401-409; doi: 10.1677/joe.0.1530401

Effect of insulin-induced hypoglycaemia on secretion patterns and rates of corticotrophin-releasing hormone, arginine vasopressin and adrenocorticotrophin in horses.

Abstract: To study the effect of hypoglycaemia on secretion rates of corticotrophin-releasing hormone (CRH), arginine vasopressin (AVP) and ACTH in a non-ruminant species, a non-surgical method was used to collect pituitary venous (PitVen) blood every 0.5 or 1 min from seven horses before and after insulin administration (0.4 U/kg i.v.). To assess the effect of PitVen cannulation on results, peripheral hormones were also measured before and after insulin in five horses without PitVen cannulae. Insulin administration lowered plasma glucose in all horses (P < 0.0001; paired t-test). Cortisol concentrations, which were similar in horses with and without PitVen cannulae before insulin, rose significantly after insulin administration in both groups. Most horses showed discomfort as glucose fell. When data from horses with and without PitVen cannulae were pooled, the peak fractional change in cortisol (Spearman's rank correlation coefficient (rs) = -0.94, P < 0.001) and the severity of hypoglycaemic symptoms (rs = -0.61, P < 0.02) were inversely ranked with the glucose nadir. In horses with PitVen cannulae, insulin administration increased secretion rates of ACTH (P < 0.0001), AVP (P < 0.0001) and CRH (P < 0.02). Increments in ACTH (rs = -0.96, P < 0.005) and CRH (rs = -0.81, P < 0.05), but not in AVP, measured during the second half-hour after insulin (i.e. the peak response), were inversely ranked with the glucose nadir. Moreover, ACTH increments were positively ranked with those in CRH (rs = 0.81, P < 0.05), but not in AVP. Nevertheless, in individual horses, minute-to-minute AVP and ACTH concentrations in PitVen blood were always correlated, whereas minute-to-minute CRH and ACTH concentrations were correlated only when glucose dropped below 3.4 mmol/l. In less hypoglycaemic horses, ACTH secretion rose despite little or no change in CRH. We suggest that in horses AVP is the primary acute signal for ACTH release both before and during hypoglycaemia; however, the increasing magnitude of ACTH increments induced by greater degrees of hypoglycaemia is determined largely by selective CRH release, which then augments corticotroph responses to AVP.
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Publication Date: 1997-06-01 PubMed ID: 9203994DOI: 10.1677/joe.0.1530401Google Scholar: Lookup
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  • Journal Article
  • Research Support
  • Non-U.S. Gov't
  • Research Support
  • U.S. Gov't
  • P.H.S.

Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

The research is about understanding how insulin-induced hypoglycemia affects the secretion rates of certain hormones in horses. It found that insulin administration led to increased secretion rates of corticotrophin-releasing hormone (CRH), arginine vasopressin (AVP), and adrenocorticotropic hormone (ACTH).

Method and Experimentation

  • The researchers conducted a non-surgical method to collect blood from the pituitary veins of seven horses every 0.5 to 1 minute before and after the administration of insulin.
  • Another group of horses were not exposed to the pituitary vein cannulation process, to compare the hormonal secretions. These were used as the control group.
  • The given insulin dosage was 0.4 U/kg, administered intravenously. This dosage successfully lowered the plasma glucose levels in all horses studied.

Results

  • The researchers detected a significant increase in cortisol concentrations after insulin administration in both groups of horses.
  • Most horses showed discomfort as glucose levels fell.
  • The degree of cortisol increase and the severity of hypoglycaemic symptoms were found to be inversely ranked with the glucose nadir (the point at which glucose levels were the lowest).
  • The administration of insulin led to increased secretion rates of ACTH, AVP, and CRH in horses with PitVen cannulae. The hormonal increments were inversely ranked with the glucose nadir.

Interpretation

  • In individual horses, minute-to-minute AVP and ACTH concentrations in PitVen blood were always correlated. However, minute-to-minute CRH and ACTH concentrations were correlated only when glucose dropped below 3.4 mmol/l.
  • In less hypoglycaemic horses, ACTH secretion rose despite little or no change in CRH.
  • The researchers suggest that in horses, AVP is the primary acute signal for ACTH release both before and during hypoglycaemia. However, the increasing magnitude of ACTH increments induced by greater degrees of hypoglycaemia is determined largely by selective CRH release, which then augments corticotroph responses to AVP.

Conclusion

  • These findings deepen the understanding of the role of hypoglycemia in the secretion rates of ACTH, AVP, and CRH in horses, and can potentially assist in the study of similar phenomena in other non-ruminant species.

Cite This Article

APA
Alexander SL, Roud HK, Irvine CH. (1997). Effect of insulin-induced hypoglycaemia on secretion patterns and rates of corticotrophin-releasing hormone, arginine vasopressin and adrenocorticotrophin in horses. J Endocrinol, 153(3), 401-409. https://doi.org/10.1677/joe.0.1530401

Publication

The Journal of endocrinology
ISSN: 0022-0795
NlmUniqueID: 0375363
Country: England
Language: English
Volume: 153
Issue: 3
Pages: 401-409

Researcher Affiliations

Alexander, S L
  • Department of Endocrinology, Christchurch Public Hospital, New Zealand.
Roud, H K
    Irvine, C H

      MeSH Terms

      • Adrenocorticotropic Hormone / blood
      • Adrenocorticotropic Hormone / metabolism
      • Animals
      • Arginine Vasopressin / blood
      • Arginine Vasopressin / metabolism
      • Blood Glucose / metabolism
      • Corticotropin-Releasing Hormone / blood
      • Corticotropin-Releasing Hormone / metabolism
      • Female
      • Horses / blood
      • Horses / metabolism
      • Hypoglycemia / metabolism
      • Hypothalamus / metabolism
      • Insulin / administration & dosage
      • Male
      • Neuropeptides / blood
      • Neuropeptides / metabolism
      • Orchiectomy
      • Pituitary Gland / metabolism
      • Secretory Rate

      Grant Funding

      • DK 38322 / NIDDK NIH HHS

      Citations

      This article has been cited 9 times.
      1. Elder E, Wong D, Johnson K, Robertson H, Marner M, Dembek K. Assessment of the hypothalamic-pituitary-adrenocortical axis function using a vasopressin stimulation test in neonatal foals.. J Vet Intern Med 2023 Sep-Oct;37(5):1881-1888.
        doi: 10.1111/jvim.16808pubmed: 37432047google scholar: lookup
      2. Yoshimura M, Conway-Campbell B, Ueta Y. Arginine vasopressin: Direct and indirect action on metabolism.. Peptides 2021 Aug;142:170555.
        doi: 10.1016/j.peptides.2021.170555pubmed: 33905792google scholar: lookup
      3. Lewandowski KC, Lewiński A, Skowrońska-Jóźwiak E, Malicka K, Horzelski W, Brabant G. Copeptin as a marker of an altered CRH axis in pituitary disease.. Endocrine 2017 Sep;57(3):474-480.
        doi: 10.1007/s12020-017-1366-6pubmed: 28795329google scholar: lookup
      4. Rendle DI, Duz M, Beech J, Parkin T, Durham AE. Investigation of single and paired measurements of adrenocorticotropic hormone for the diagnosis of pituitary pars intermedia dysfunction in horses.. J Vet Intern Med 2015 Jan;29(1):355-61.
        doi: 10.1111/jvim.12489pubmed: 25312676google scholar: lookup
      5. Hart KA, Barton MH. Adrenocortical insufficiency in horses and foals.. Vet Clin North Am Equine Pract 2011 Apr;27(1):19-34.
        doi: 10.1016/j.cveq.2010.12.005pubmed: 21392651google scholar: lookup
      6. Roper J, O'Carroll AM, Young W 3rd, Lolait S. The vasopressin Avpr1b receptor: molecular and pharmacological studies.. Stress 2011 Jan;14(1):98-115.
        doi: 10.3109/10253890.2010.512376pubmed: 20828336google scholar: lookup
      7. Keenan DM, Alexander S, Irvine C, Veldhuis JD. Quantifying nonlinear interactions within the hypothalamo-pituitary-adrenal axis in the conscious horse.. Endocrinology 2009 Apr;150(4):1941-51.
        doi: 10.1210/en.2008-1249pubmed: 19022882google scholar: lookup
      8. Aguilera G, Subburaju S, Young S, Chen J. The parvocellular vasopressinergic system and responsiveness of the hypothalamic pituitary adrenal axis during chronic stress.. Prog Brain Res 2008;170:29-39.
        doi: 10.1016/S0079-6123(08)00403-2pubmed: 18655869google scholar: lookup
      9. Lolait SJ, Stewart LQ, Jessop DS, Young WS 3rd, O'Carroll AM. The hypothalamic-pituitary-adrenal axis response to stress in mice lacking functional vasopressin V1b receptors.. Endocrinology 2007 Feb;148(2):849-56.
        doi: 10.1210/en.2006-1309pubmed: 17122081google scholar: lookup
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