A biologically active lipid, thromboxane, as a regulator of angiogenesis and lymphangiogenesis.

Thromboxane (TX) and prostaglandins are metabolites of arachidonic acid, a twenty-carbon unsaturated fatty acid, and have a variety of actions that are exerted via specific receptors. Angiogenesis is defined as the formation of new blood vessels from pre-existing vascular beds and is a critical component of pathological conditions, including inflammation and cancer. Lymphatic vessels play crucial roles in the regulation of interstitial fluid, immune surveillance, and the absorption of dietary fat from the intestine; and they are also involved in the pathogenesis of various diseases. Similar to angiogenesis, lymphangiogenesis, the formation of new lymphatic vessels, is a critical component of pathological conditions. The TP-dependent accumulation of platelets in microvessels has been reported to enhance angiogenesis under pathological conditions. Although the roles of some growth factors and cytokines in angiogenesis and lymphangiogenesis have been well characterized, accumulating evidence suggests that TX induces the production of proangiogenic and prolymphangiogenic factors through the activation of adenylate cyclase, and upregulates angiogenesis and lymphangiogenesis under disease conditions. In this review, we discuss the role of TX as a regulator of angiogenesis and lymphangiogenesis, and its emerging importance as a therapeutic target.

Changes in blood pressure, blood flow towards the head and heart rate during 90 deg head-up tilting for 30 min in anaesthetized male rats.

NEW FINDINGS: What is the central question of this study? How does the baroreceptor reflex contribute to systemic blood pressure (BP) control during prolonged 90 deg head-up tilting (HUT) in unconscious rats? What is the main finding and its importance? In intact rats, heart rate (HR) increased after the transition to upright by HUT, and BP was maintained in this posture throughout the 30 min experimental period. After sinoaortic denervation, which results in lack of discharge of the baroreflex afferents, HR and BP decreased gradually during 30 min of 90 deg HUT, suggesting that the baroreceptor reflex is an important factor for maintenance of BP during long-term upright posture. Changes in cardiovascular parameters during prolonged 90 deg head-up tilting (HUT) in animals have not been elucidated in detail. We clarified changes in systemic blood pressure (BP), blood flow towards the head (BF) and heart rate (HR) and the role of the baroreceptor reflex after a transition from the supine posture to 90 deg HUT for 30 min in anaesthetized rats (n = 13). In control rats with the baroreceptor reflex afferents intact, mean BP and BF after the onset of 90 deg HUT decreased significantly by -15.4 ± 5.9 and -26.2 ± 11.5% at 2.9 ± 1.1 s (mean ± SD, n = 12), respectively, compared with control values and then immediately increased and steadied at 30.7 ± 13.1 s (plateau; -2.8 ± 8.5% in BP and -17.5 ± 17.4% in BF compared with control values; BP was maintained during 90 deg HUT). After acute sinoaortic denervation in seven rats, initial reductions in BP and BF after 90 deg HUT were observed at 3.9 ± 1.0 s, similar to the reductions in the nerve-intact rats; the percentage changes from control were -19.2 ± 3.7 and -32.3 ± 8.4%, respectively. These parameters reached a plateau at 22.4 ± 5.8 s at -8.6 ± 7.7 and -29.5 ± 15.0%, respectively, and then BP decreased gradually throughout 90 deg HUT. Heart rate increased slightly after 90 deg HUT in nerve-intact rats, but after sinoaortic denervation this increase disappeared and HR decreased gradually during 90 deg HUT. These results suggest that the baroreceptor reflex contributes to the maintenance of adequate BP during long-term 90 deg HUT.