The Effect of Thromboxane on Contraction of Canine Mesenteric and Lingual Arteries

Abstract

Thromboxane A2 (TXA2), a potent vasoconstrictor agent, is released from platelets and smooth muscle during inflammation and trauma. TXA2 may cause lingual artery (LA) contraction, leading to lingual paresthesia. The effects of U-46619, a TxA2 mimetic, on isolated rings of canine LA and mesenteric artery (MA) were examined. U-46619 (1 nmol/L to 1 mumol/L) caused a triphasic contraction of LA and MA; a rapid, phasic contraction; a slow, sustained contraction; and, upon washout of U-46619, a maintained contraction. The MA relaxed slowly, but the LA remained contracted for at least three h after washout. Decreasing extracellular calcium ion (Ca2+o) to less than 0.1 mumol/L with 2 mmol/L EGTA relaxed MA, but not LA. EGTA (4 mmol/L) partially relaxed the maintained contraction of LA. Inhibition of protein kinase C with amphotericin B or staurosporine inhibited the phasic and sustained contractions of LA, but did not affect the maintained contraction in the presence or absence of EGTA. Thus, CA2+o was required for the initial contraction of the LA by U-46619, but did not appear to be required for the maintained contraction following washout of U-46619. The data support the conclusion that following a brief exposure to U-46619, maintained contraction of LA persists by a unique mechanism that may be independent of Ca2+ and protein kinase C. Sustained LA contraction after exposure to endogenous TXA2 during inflammation and trauma may contribute to impaired lingual blood flow and orofacial tissue injury.

Bronchial Muscle Peristaltic Activity in the Fetal Rat

“…The use of the thromboxane A 2 agonist U46619 to stimulate phasic contractions in this study was necessary to induce consistent and reproducible phasic activity to allow further evaluation of its mechanism. Aside from its powerful smooth muscle tonic contraction response, U46619 has been shown by others to induce phasic activity in the thoracic duct (11), coronary arteries (24), and dog lingual and mesenteric arteries (25). Of interest is the fact that following KCl stimulation the fetal bronchial muscle develops tonic force without phasic contractions suggesting that the mechanism by which U46619 induces rhythmic activity does not depend on the tonic force.…”

Acid–base and electrolyte balance following administration of three crystalloid solutions in dogs undergoing elective orthopaedic surgery

“…Non‐adjacent vessels were used for each sample to avoid local changes in vascular supply (Greenberg et al. ). Blood samples were taken through IV catheters in one dog from each group, but significant findings were not altered by inclusion of these data.…”

The following is the abstract of the article discussed in the subsequent letter:

“…Greenberg et al (4) reported that the lingual artery in dogs has a very different response to the stimulation of calcium influx than the mesenteric artery or other vessels. Moreover, Tsukada and Chiba (13) showed a depressed vasoconstrictive effect of norepinephrine on the lingual artery that was not reproducible in the mesenteric vessels when they were submitted to changes in temperature.…”