Hiromichi Tsuru

Responsiveness of isolated dog veins to bradykinin and other bioactive peptides: distribution of sensitivity to bradykinin and possible correlation with genesis of the venous system.

Contractile responses of isolated dog veins to bradykinin were studied. Responses to norepinephrine were taken as standards. According to their sensitivity to bradykinin, the veins obtained from 14 sites of the venous system were divided into two groups, while all the veins were almost uniform in their sensitivity to norepinephrine. One group has high sensitivity to bradykinin and the other has low sensitivity. The former includes the pulmonary, hepatic, splenic, and portal veins, the anterior vena cava, and the upper and the middle divisions of the posterior vena cava. The latter includes the external jugular, cephalic, azygos, femoral, and saphenous veins, and the lower division of the posterior vena cava. The responses of the renal vein were intermediate. A striking correlation was noted between the distribution of bradykinin sensitivity and the genesis of the venous system. Five bioactive peptides other than bradykinin were also studied. Only angiotensin induced contraction in some preparation, but, as a whole, caerulein, eledoisin-related peptide, oxytocin and vasopressin rarely showed contractile activity.

Differences in the Response of Three Embryologically Distinct Segments of the Isolated Canine Posterior Vena cava to Vasoactive Substances

The canine posterior vena cava was excised and divided into three embryologically distinct segments: segment A (supradiaphragm), segment B-C (intrahepatic and that between liver and renal veins), and segment D (infrarenal). Circular and longitudinal strips were cut from each segment, suspended in Krebs bicarbonate solution and isometric tensions were recorded. The responses to six vasoactive agents, as well as transmural neural stimulation were studied. Maximum tension and ED50 were obtained for norepinephrine, epinephrine, acetylcholine, bradykinin, histamine and 5-hydroxytryptamine (5-HT). The responses were not only quantitatively, but qualitatively different among the three segments. Bradykinin constricted the strips in A and B-C but not in D. 5-HT (less than 10(-5) M) caused a dose-dependent contraction in A and D through its direct stimulating action, while in C, a contractile response appeared only after administration of a higher dose of 5-HT. This was due to an indirect sympathomimetic action of the agent. Segment B-C, which histologically contained massive longitudinal muscle bundles in the outer layer of the wall, exhibited spontaneous, rhythmic contractions. The existence of a cholinergic excitatory innervation, in addition to adrenergic, was demonstrated in C by transmural neural stimulation.

Structure-activity relationship of the cardenolide, with special reference to the substituents and configurations at C-14 and C-15

Es wurden die kardiotonischen Wirkungen sechs neuer Derivate von 14-Deoxy-14βH-digitoxigenin und 14-Deoxy-14β-chloro-digitoxigenin auf das isolierte Froschherz untersucht, sowie die Beziehungen zwischen deren chemischen Strukturen und Wirkungen diskutiert.

Presynaptic sympathetic supersensitivity following long-term preganglionic denervation.

After chronic preganglionic denervation of the rabbit ear artery, the contractile response to low frequency stimulation of the postganglionic innervation is increased. A preliminary analysis suggests that this cannot be accounted for by effector cell changes, but is due to an increase in adrenergic transmitter release.

Relaxation of isolated rabbit veins mediated by latent histamine H2-receptors.

Isolated rabbit veins preconstricted by either norepinephrine, methoxamine or potassium were relaxed by histamine in the presence of mepyramine, a histamine H1-antagonist. The relaxation was not antagonized by atropine, propranolol and indomethacin but by an H2-antagonist cimetidine. It is likely that histamine relaxes the rabbit veins through H2-receptors.

Structure-activity relationship of the cardenolides derived from digoxigenin and digitoxigenin, with special reference to the configuration at C-5

Es wurden die kardiotonischen Wirkungen des Digoxigenins, sowie deren 5 Derivate, einschliesslich des 5α-Digoxigenins, auf das isolierte Forschherz untersucht und Vergleiche mit den entsprechenden Aglykonen der Digitoxigenin-Reihe gezogen.

Cardiotonic activities of some new type of bufadienolide- and cardenolide-conjugates

Some new type of bufadienolide-and cardenolide-conjugates, including bufotoxins and 3-sulfates recently isolated from the toad skin, were tested for their cardiotonic activities by using isolated frog hearts and guinea-pig atria. The relative potencies were obtained and reported.

Cardiotonic activities of 3,5-seco-4-nor-cardenolides inRana nigromaculata

Die cardiotonische Aktivität von 4 neuen, aus Digitoxigenin hergestellten 3,5-Seco-4-norcardenoliden auf das isolierte Froschherz wurde geprüft. Die Ergebnisse zeigen, dass für die positive inotrope Wirkung eines Cardenolids das intakte Steroidgerüst nicht notwendig ist.