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Cyclooxygenase protein expression is increased post-suspension in Male SD rats  L.T.Coats, D.Eatman, M. Walton, A. Beasley, M.A. Bayorh. Department of Pharmacology / Toxicology, Morehouse School of Medicine and Georgia State University, Atlanta, GA

   Recently it has been noted that orthostatic intolerance has become a common symptom experienced by astronauts. The purpose of this study was to determine whether the reduction in blood pressure post-suspension seen in rats may be due, to changes in Nitric Oxide Synthase (NOS) / Cyclooxygenase (COX) protein expression. Using the Head-down tilt (HDT) model, we examined the effects of short-term suspension on mean arterial pressure, and tissue NOS and COX protein expression in male SD rats.  Blood pressure was measured in male Sprague Dawley rats prior to, during and upon release from suspension. During hindlimb unloading the heart rate and blood pressure remained constant; however, upon release from suspension blood pressure decreased significantly when compared to non-suspended rats. Using Western Blot analysis, NOS-2, NOS-3, and COX-1 was measured in kidney and heart samples. COX-1 and NOS- 2 were elevated in kidney but remained unchanged in the heart when compared to non-suspended rats. In addition, COX-2 was greater in heart samples but remained unchanged in the kidneys. NOS-3 remained unchanged following suspension when compared to non-suspend.

Taken together, the reduction in blood pressure observed post-suspension in rats may be due to increased production of nitric oxide and vasodilatory prostaglandins caused by the upregulation of COX and NOS. This research was supported by NASA grant NCC 9-112.