Prolonged hemorrhagic shock decreases splanchnic prostacyclin synthesis

Area of Science:

• Physiology
• Biochemistry
• Pharmacology

Background:

• Hemorrhagic shock can induce significant physiological changes.
• Prostanoids, including prostacyclin, play crucial roles in regulating vascular tone and organ function.
• The splanchnic circulation's response to shock requires further elucidation.

Purpose of the Study:

• To investigate the impact of increasing durations of hemorrhage-induced hypotension on basal splanchnic prostanoid release.
• To determine the time-dependent capacity of the superior mesenteric artery and intestine (SV + SI) to release prostanoids during shock.

Main Methods:

• Male Sprague-Dawley rats were subjected to hemorrhage to 30 mm Hg for 30, 60, or 120 minutes.
• Following shock, the SV + SI was perfused in vitro, and basal release of 6-keto-PGF1 alpha, PGE2, and thromboxane B2 was measured via radioimmunoassay.
• Results were compared to sham-operated controls.

Main Results:

• 6-keto-PGF1 alpha was the predominant prostanoid released from control SV + SI.
• A 30-minute shock period significantly increased 6-keto-PGF1 alpha release compared to controls.
• Longer shock durations (60 or 120 minutes) reduced the release of all measured prostanoids below control levels.

Conclusions:

• The splanchnic circulation attempts to compensate for short-term hemorrhagic shock by increasing prostacyclin release.
• The capacity for increased endogenous prostacyclin release is limited by the duration of hypotension.
• Prolonged hemorrhagic shock impairs the splanchnic circulation's ability to produce key vasodilatory prostanoids.