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Alternative Strategy for Stress Tolerance: Opioids

¹ Department of Zoology & Physiology.
² Department of Kinesiology & Health, University of Wyoming, Laramie.
³ School of Medicine, University of Washington, Seattle.
⁴ College of Medicine, University of Kentucky, Lexington.

Address correspondence to Joan Smith Sonneborn, Zoology & Physiology Department, University of Wyoming, Laramie, WY 82071-3166. E-mail: cancun{at}uwyo.edu

Endogenous opioids have been implicated in the pathway of tolerance to stresses. Hibernating tissues tolerate stress. Serum from hibernating woodchucks (hibernation induction trigger [HIT]), from summer nonhibernating animals (summer woodchuck active plasma [SWAP], and potential "hibernation opioid mimics" (D-Ala² D Leu⁵ Enkephalin [DADLE]), and Deltorphin D (Delt D) were used as ischemic preconditioning agents (IPC) in an in vivo surgically induced cardiac ischemia rat model. Comparison of the IPC treatment was monitored by the molecular intensity of stress transcripts for polyubiquitin and HSP70 in Northern blot analyses. Delt D and HIT significantly reduced total polyubiquitin transcript expression, 2.1-fold and 1.4-fold, respectively, in ischemic tissue, while SWAP and DADLE did not differ from saline controls. The Delt D effect was sensitive to glibenclamide (Glb), a K_ATP (potassium adenosine triphosphate) channel blocker. No inducible HSP70 was detected. The demonstration of an opioid IPC modulation of the ubiquitin stress pathway found here may be relevant for development of drug intervention in heart attacks and stroke.