Heat acclimation and hypohydration in aged rats: The involvement of adrenergic pathways in thermal-induced vasomotor responses in the portal circulation

Mara Shochina, Walid Haddad, Uri Meiri, Michal Horowitz*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

8 Scopus citations

Abstract

1. The beneficial effects of heat acclimation on thermal induced vasomotor responses of hypohydrated aged rats were assessed by measuring the isometric tension of aortic and portal rings of old and young rats under heat acclimation and hypohydration in response to α-adrenergic (α-AR) and β- adrenergic (β-AR) stimulation (phenylephrine 10-9-10-2 mM and isoprenaline 10-9-10-4 respectively). In parallel, portal blood flow (PBF), which drains the splanchnic vasculature, was measured in conscious rats, before and during heat stress (42°C). 2. In the aorta, heat acclimation augmented phenylephrine (α-AR) induced tension, to a great extent in the older rats. Hypohydration increased α-AR sensitivity in all experimental groups. Acclimation and aging brought about decreased responsiveness in isoprenaline induced relaxation (β-AR) in both the aorta and the portal vein. Hypohydration increased β-AR responsiveness in the portal vein of OR, acclimated and acclimated-hypohydrated rats. 3. Normothermic euhydrated resting PBF was similar for young and old rats. Hypohydration decreased resting PBF. Upon heat stress, thermal induced vasoconstriction in hypohydrated YR and OR occurred earlier than in the euhydrated groups and was more pronounced. The latter responses were attenuated in the old rats. 4. Taken together, these results imply that chronic environmental stressors such as heat acclimation and hypohydration produce selective alterations in AR responsiveness of the vasculature in both young and old rats. Consequently, thermoregulatory vasomotor mediated mechanisms, as exhibited in this study in PBF, may differ in their responsiveness in these two age groups.

Original languageEnglish
Pages (from-to)289-295
Number of pages7
JournalJournal of Thermal Biology
Volume21
Issue number5-6
DOIs
StatePublished - Oct 1996

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