Angiotensin II relaxation of rainbow trout vessels in vitro

The effects of salmonid angiotensin II ([Asn1,Val5]ANG II) were examined in isolated trout arteries [celiacomesenteric (CMA), coronary (COA), 3rd or 4th gill arch epibranchial (EBA), ventral aorta (VA)] and veins [anterior cardinal (ACV) and ductus Cuvier strips (DOC)]. ANG II (10(-10)-10(-6) M) produced modest (< 50% other agonists) transient contractions in otherwise unstimulated COA but was a poor agonist in other vessels. In precontracted vessels, ANG II responses were triphasic; transient contraction (P1), relaxation (P2), and partial recovery (P3) and vessel specific. P1 was similar to uncontracted vessels. With 10(-6) MANG II, %P2 was: EBA, 60.3 +/- 8.3% (n = 22); CMA, 48.8 +/- 8.8% (n = 4); ACV, 38.8 +/- 5.3% (n = 29); VA, 29.4 +/- 4.9% (n = 8); DOC, 25.5 +/- 2.4% (n = 14); COA, 13.2 +/- 6.7% (n = 4). P2 in EBA and ACV was dose dependent [EBA vs. ACV: mean effective concentration (EC50) = 3.6 x 10(-9) +/- 8.1 x 10(-10) M, n = 7 vs. 6.2 x 10(-8) +/- 2.3 x 10(-8) M, n = 8, respectively; P < or = 0.05] and inhibited by indomethacin but unaffected by propranolol, NG-monomethyl-L-arginine, saralasin, PD-123177, or DuP-753. Removal of EBA endothelium also inhibited relaxation. By comparison, ANG II did not relax bullfrog arteries (dorsal aorta, systemic arch, CMA) or femoral veins. These results show that, in large vessels of trout, the predominant effect of ANG II is an endothelium-dependent, prostanoid-mediated relaxation that is unaffected by classical ANG II-receptor antagonists.(ABSTRACT TRUNCATED AT 250 WORDS)

Contraction of reptile, amphibian, and fish blood vessels by endothelin-1

Endothelin-1, a 21 aminio acid peptide originally isolated from porcine endothelial cells, has been reported to contract arteries and veins from several mammalian species. We studied the effect of endothelin-1 on blood vessels removed from turtle (Pseudymes scripta), frog (Rana pipiens), and catfish (Amiurus melas). The vessels were suspended for isometric recording in thermally controlled organ baths and were exposed cumulatively to endothelin-1 (0.5–100 nM). All vessels showed a concentration-dependent increase in isometric force. The half-maximal concentrations (EC50) of endothelin-1 were all in the nanomolar range: turtle left systemic arch (17.9 ± 1.2 nM), frog systemic arch (5.5 ± 1.1 nM), catfish mesenteric artery (6.3 ± 1.3 nM), and catfish posterior cardinal vein (2.5 ± 1.4 nM). Vessels from frog and catfish developed more tension when exposed to 100 nM endomelin-1 than to 80 mM KCl (ET/KCl tension ratio). Our observations that endothelin-1 potently contracts blood vessels from reptiles, amphibians, and fish suggest that endothelin-1 may be a vertebrate peptide mat has been conserved during evolution.Key words: endothelium-derived contracting factor, vascular smooth muscle, vasoactive peptide.

The mechanics of lung ventilation and the effects of hypercapnia on respiration in Bufo marinus

Respiratory and circulatory changes associated with exposure to elevated ambient carbon dioxide (CO2) levels were studied in free-moving Bufo marinus. The buccal cavity, lungs, and systemic arch were cannulated singly or in various combinations. Simultaneous recordings from the lungs and buccal cavity permitted analysis of respiratory rate and pattern, while systemic cannulae provided constant blood-pressure measurements. All experiments were conducted at 22 °C.Normal breathing patterns consisted of continuous buccal 'oscillations' with irregularly occurring lung 'ventilations' and occasional high pressure 'inflations.' On exposure to increased ambient CO2 levels, oscillations decreased, ventilations increased, and inflations predominated, resulting in an overall increase in lung minute-volume. Systemic pressure decreased as ambient CO2 approached 3%, but returned to normal, with an associated increase in heart rate, at the 5% level. It is postulated that the ventilatory and concomitant circulatory responses are mediated by receptors functioning in both the chemoreceptive and baroreceptive modes.

A mechanism for the selective distribution of blood in the amphibia

Pulse pressures were measured in 23 Amphiuma tridactylum. It was found that the pulmonary artery had a lower diastolic blood pressure than did the systemic arch. There was a slight pulse lag in the systemic arch when compared to the pressure rise in the pulmonary artery such that a pressure rise was not recorded in the systemic arch until the blood pressure in the two circuits became equal. It was suggested that the pulse lag could account for deoxygenated blood being primarily shunted to the pulmonary circuit, and oxygenated blood being shunted to the systemic circuit.

A SYSTEMATIC STUDY OF THE MAIN ARTERIES IN THE REGION OF THE HEART—AVES VIII: ANSERIFORMES. PART I

Seventeen species of the order Anseriformes were dissected and diagrams of the arrangement-patterns of the main arteries of the neck and thorax prepared. All specimens were found to be bicarotidinae normales. Both the right ligamentum aortae and the left ligamentum botalli were present in all of the forms that were studied. Three new vessels were found in several species of ducks. The allantoic artery arises as a branch of the left ischiadic artery in the embryonic Canada goose. The left radix aortae forms an anastomosis with the left pulmonary arch after atrophy of the left systemic arch. The left ductus botalli atrophies after this anastomosis and disappears almost entirely by the time the bird hatches.