Norepinephrine induced contractions of the feline mesenterial vein under oxygenized and hypoxic conditions in vitro.
Cylindrical segments from mesenteric veins of 8 cats were prepared and mounted in a Krebs-Ringer tissue bath. The oxygenized solution was bubbled with 95% O2 and 5% CO2. For lowered oxygen tension 95% N2 and 5% CO2 was used. Intraluminal pressure was changed between 0-20-0 mm Hg in consecutive cycles at a rate of 0.93-1.33 mm Hg/sec. Outer radii on the upward routes were recorded. Norepinephrine was added in doses of 6 X 10(-8) -6 X 10(-5) M, first in the oxygenized medium then under hypoxic conditions, and then in oxygenized medium again. Maximally relaxed curves were taken with 1.5 X 10(-4) M papaverine at the end of the experiment. Outer radius of relaxed segments at 20 mm Hg intraluminal pressure was 2.03 +/- 0.12 mm which slowly dilated to 2.09-0.12 mm toward the end of the experiment, and reached 2.11 +/- 0.11 mm with papaverine. Maximum active contractions of the outer radii were found at 6 mm Hg intraluminal pressure and with 6 X 10(-5) M norepinephrine in the bath: 23.1 +/- 3.2% in oxygenized, 20.3 +/- 3.4% in hypoxic and 19.0 +/- 3.4% again in oxygenized media. The observations showed that acute hypoxia had no or had only a limited effect on the contraction of the feline mesenteric vein.
Nádasy
G L
GL
Experimental Research, Semmelweis University Medical School, Budapest, Hungary.
Polenov
S
S
Chernyavskaya
G
G
Monos
E
E
Hamar
J
J
Kovách
A G
AG
D000818:Animals; D002415:Cats; D005260:Female; D066298:In Vitro Techniques; D008297:Male; D008642:Mesenteric Veins / Q000187:drug effects*; D009638:Norepinephrine / Q000494:pharmacology*; D010100:Oxygen / Q000494:pharmacology*; D014661:Vasoconstriction / Q000187:drug effects*
D010100:Oxygen; D009638:Norepinephrine