Effect of muscle length on the in vitro comparison of femoral arteries before and after endotoxin shock.
Control and endotoxin-treated femoral arteries were compared in vitro for the effect of muscle length. Rats were anesthetized with pentobarbital, and endotoxin (6 mg/kg) was infused for 1 h. A control ring before endotoxin treatment and a ring after endotoxin treatment (blood pressure = 40 mmHg) were excised from the contralateral artery for length-tension and dose-response experiments with phenylephrine. The initial length for resting tension (Li) was shorter for endotoxic rings (1.23 +/- 0.01 vs. 1.41 +/- 0.02 mm in control), but the length of maximum active tension (Lmax) was the same. In length-tension experiments the values for active tension (6.36 +/- 0.61 vs. 4.06 +/- 0.60 x 10(3) dyn/cm), preload at Lmax (1,333 +/- 204 vs. 733 +/- 146 mg), and passive stiffness were increased after endotoxin. In dose-response experiments at the same preload, the endotoxic rings had a lower active tension (3.28 +/- 0.28 vs. 6.55 +/- 0.27 x 10(3) dyn/cm) but the same sensitivity. At Lmax, active tension (12.45 +/- 0.48 vs. 5.01 +/- 0.89 x 10(3) dyn/cm in control vessels) and sensitivity (half-maximum effective dose = 0.68 +/- 0.8 x 10(-6) vs. 1.39 +/- 0.29 x 10(-6) M in control vessels) were greater for endotoxic rings. These experiments show that phenylephrine sensitivity and active tension in the rat femoral artery are increased by endotoxin shock, and the importance of muscle length is implied.
Zhou
Z
Z
Department of Physiology and Biophysics, University of South Florida, Tampa 33612.
Price
J M
JM
Sutton
E T
ET
Baker
C H
CH
D000818:Animals; D001794:Blood Pressure; D004305:Dose-Response Relationship, Drug; D004731:Endotoxins / Q000494:pharmacology; D005263:Femoral Artery / Q000187:drug effects / Q000503:physiopathology*; D066298:In Vitro Techniques; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000503:physiopathology*; D010656:Phenylephrine / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012016:Reference Values; D012772:Shock, Septic / Q000503:physiopathology*; D013314:Stress, Mechanical; D014661:Vasoconstriction
D004731:Endotoxins; D010656:Phenylephrine