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PubMed1992

Suppression of intestinal smooth muscle contraction by phenolic compounds.

Wood creosote, a mixture of guaiacol, creosol, and other related phenolic compounds, suppresses the spontaneous longitudinal phasic contractions of an isolated rat ileal segment. Thirty-two phenolic compounds were screened for this activity to identify the active substances in wood creosote. Of the 32 compounds tested, 2,3,6-trimethylphenol, 2,4,6-trimethylphenol, and 4-ethylguaiacol were most effective and their respective IC50 values were 0.035, 0.037, and 0.043 mM. Guaiacol and creosol, the chief constituents of wood creosote, were moderately effective and their respective IC50 values were 0.18 and 0.13 mM. Other phenolic compounds in wood creosote also suppressed the ileal contraction although their IC50 values differed markedly from each other. These results suggest that practically all of its constituent phenolic compounds contribute to wood creosote's capacity to suppress ileal contraction.

Animals↗
PubMed2004

Nitrergic mechanisms mediating inhibitory control of longitudinal smooth muscle contraction in mouse small intestine.

Studies using genetic manipulation to investigate mechanisms of control of physiologic function often necessitate mouse models. However, baseline functional analysis of murine small intestinal motility has not been well defined. Our aim was to define nitrergic mechanisms regulating mouse small intestinal longitudinal muscle. Endogenous nitric oxide (NO) is an important neuroregulatory substance mediating inhibition of contractile activity in murine small bowel. Full-thickness muscle strips of jejunum and ileum from C57BL/6 mice (n > or =6 mice) cut in the direction of longitudinal muscle were studied. Numerous conditions of electrical field stimulation (EFS) and effects of exogenous NO and NO donors were studied in the absence or presence of inhibitors of nitric oxide synthase (NOS) and 1H-[1,2,4]-oxadiazaolo-[4,3-a]-quinoxalin-1-one (ODQ), a downstream inhibitor of guanylyl cyclase. EFS induced a frequency-dependent inhibition of contractile activity in both jejunum and ileum (P < 0.05). As the voltage of EFS was increased, inhibition turned to excitation in the jejunum; in contrast, the ileum demonstrated a voltage-dependent increasing inhibition (P < 0.05 each). EFS-induced inhibition was blocked by NOS inhibitors and ODQ. NO donors inhibited spontaneous contractile activity abolished by ODQ. NO appears to be an endogenous inhibitory neurotransmitter in murine longitudinal small bowel muscle. Nitrergic mechanisms mediate inhibitory control of murine longitudinal small intestinal muscle. Differences exist in neuroregulatory control between jejunum and ileum that may be related to their known difference in motor patterns.

Animals↗
PubMed2006

Cardiovascular responses induced during high-intensity eccentric and concentric isokinetic muscle contraction in healthy young adults.

The purpose of this study was to determine the differences in cardiovascular response between high-intensity eccentric (ECC) and concentric (CON) contractions, and to obtain the basic data applicable to resistance training in middle-aged and elderly individuals. The subjects who participated in this study were nine healthy men (age 24.1 +/- 1.3 years). ECC and CON were randomly selected, as each test consisted of a high-intensity (80% of peak torque) bout of 60 s of ECC and CON isokinetic contractions of the flexor carpi radialis. Systolic pressure (SBP), diastolic pressure (DBP) and heart rate (HR) during ECC and CON were measured using a Finometer. Mean arterial pressure (MAP) was calculated by SBP and DBP. Rate-pressure product (RPP) was calculated by SBP and HR. SBP, DBP, MAP and RPP during ECC were significantly smaller compared with CON. It is clear that cardiovascular response by high-intensity contraction is smaller in ECC than in CON. High-intensity ECC has been suggested to exert only small stress to the cardiovascular system. Thus, being a contraction mode it may be applicable to resistance training.

Adult↗
PubMed2004

Peroxynitrite inhibits relaxation and induces pulmonary artery muscle contraction in the newborn rat.

Nitric oxide (NO) reacts with superoxide anion to form the peroxynitrite anion (ONOO-), a molecule with pulmonary vasodilator properties in the adult rat. The purpose of this study was to compare the effects of ONOO- on intrapulmonary arteries from the newborn (days 4-7), juvenile (day 14), and adult rat. Following thromboxane A2 (TXA2) analogue (U46619) prestimulation, newborn vessels were more sensitive to ONOO- -induced muscle contraction, compared to both the juvenile and the adult vessels. Peroxynitrite-induced contraction in newborn vessels was abrogated by ibuprofen, an endothelin B-receptor blocker (A-192621), or a rho-kinase-specific inhibitor (Y27632) (all p < 0.01). Following KCl stimulation and TXA2 receptor blockade, ONOO- induced NO-dependent muscle relaxation in newborn vessels via stimulation of the endothelial and inducible nitric oxide synthases. However, in the presence of ONOO-, the pulmonary artery relaxation response to endothelium-dependent stimulation was significantly reduced (p < 0.01). Finally, newborn but not adult pulmonary arteries exposed to ONOO- showed a 10-fold increase in 8-isoprostane production, a possible mediator of ONOO- -induced contraction. We conclude that exposure to ONOO- results in a unique response in newborn intrapulmonary arteries characterized by increased 8-isoprostane generation, which we believe is responsible for its vasoconstrictor effect. This unique response potentially renders the newborn more susceptible to ONOO- -induced pulmonary hypertension than older animals.

Aging↗