ROLE OF PROSTAGLANDINS IN REGULATION OF BLOOD-FLOW AND MODULATION OF SYMPATHETIC VASOCONSTRICTION IN NORMAL AND ACUTELY INFLAMED RABBIT KNEE JOINTS

Experiments were performed to investigate, in the normal and acutely i nflamed rabbit knee joint, the role of prostaglandins in the regulatio n of joint blood flow, measured by laser Doppler flowmetry, as well as their modulation of sympathetic vasoconstriction. Close intra-arteria l injection of prostaglandin E(2) (PGE(2)) produced a dose-dependent v asodilatation in control joints, but the responses in inflamed joints were much smaller. Close intra-arterial infusion of indomethacin signi ficantly increased the responses of the control joints to PGE(2), but had no effect on the responsiveness of the inflamed joints. Nerve-medi ated vasoconstrictor responses did not change significantly with close intra-arterial infusion of indomethacin, either in control or in infl amed joints. Indomethacin infusions decreased basal joint blood flow i n the control joint significantly more than in the inflamed joint. The systemic blood pressure was elevated slightly only in the control gro up. The results of this study show that although prostaglandins have a role to play in regulation of basal blood flow in both normal and acu tely inflamed rabbit knee joints, they do not appear to play a signifi cant role in modulation of sympathetic vasoconstrictor responses. Pros taglandin E(2) receptors are functional in normal knee joint blood ves sels, but they may be disabled by the process of inflammation.