Affiliations: Department of Plastic Surgery, Military Hospital – State Health Centre, Budapest, Hungary | Department of Pathophysiology, Semmelweis University, Budapest, Hungary | First Department of Obstetrics and Gynecology, Semmelweis University, Budapest, Hungary | Department of Physiology and Gerontology and Szentagothai Res Centre, University of Pécs, Pécs, Hungary | Department of Physiology New York Medical College, Valhalla, NY, USA
Note: [] Corresponding author: Akos Koller MD, Ph.D, Department of Physiology, New York Medical College, Valhalla, NY 10595, USA; Department of Pathophysiology and Gerontology, University of Pécs, Medical School, 7622 Pécs, Hungary. Tel.: +1 914 594 4085; Fax: +1 914 594 4018; E-mail: [email protected]
Abstract: We aimed to test two hypotheses: 1) isolated small veins develop substantial myogenic tone in response to elevation of intraluminal pressure, 2) H2O2 contributes to the mediation of myogenic response via activation of arachidonic acid (AA) cascade and release constrictor prostaglandins. METHODS: Small veins were isolated from gracilis muscle of male rats, then cannulated. Changes of diameter to increases in intraluminal pressure, H2O2 and arachidonic acid in the presence and absence of various inhibitors were measured by videomicroscope and microangiometer. At the end of experiments the passive diameter were obtained in Ca2+-free PSS solution. RESULTS: Isolated rat gracilis muscle small veins developed a substantial myogenic tone in response to increases in intraluminal pressure (1–12 mmHg). Calculated maximum myogenic tone was 70 ± 5% at 10 mmHg. Presence of catalase or indomethacin or SQ 29,548 reduced significantly the pressure-induced myogenic response. Also, H2O2 (10−9–10−5 M) and arachidonic acid (10−7–10−4 M) elicited concentration dependent constrictions, which were inhibited by the presence of indomethacin or SQ 29,548. CONCLUSION: We propose that both myogenic response and pressure-induced release of H2O2 play important roles in regulating the vasomotor function of venules both in physiological and pathological conditions.
