Tocolytic effects of a long-acting beta2-adrenoceptor agonist, formoterol, in rats

Comparison of effects of formoterol and BRL 37344 on isolated term-pregnant rat myometrial strips in vitro

This study was designed to compare the effects of beta-adrenoceptor agonists formoterol and BRL 37344 on spontaneous contractions and the levels of cAMP and cGMP of myometrial strips isolated from timed-pregnant rats. Myometrial strips were obtained from term-pregnant Wistar albino rats (n=12), mounted in organ baths and tested for changes in isometric tension in response to formoterol and BRL 37344. We evaluated the effect of increasing concentrations of formoterol and BRL 37344 on oxytocin-induced myometrial contractions and on contractions of myometrial smooth muscle pretreated with metoprolol, ICI 118.551 and SR 59230A (beta1, beta2, beta3-adrenoceptor antagonist, respectively, 10(-6) M). Effects of formoterol and BRL 37344 on cAMP and cGMP levels in isolated myometrial strips (n=6) were evaluated by radioimmunoassay kits. Formoterol (10(-12)-10(-8) M) and BRL 37344 (10(-11)-10(-5) M) concentration-dependently decreased the amplitude of oxytocin-induced contractions. E(max) value (100%) of formoterol was increased significantly more than E(max) value (70.6%) of BRL 37344 (P<0.05), with no change in pD(2) value (9.54+/-0.12 and 9.12+/-0.12, respectively). The inhibition of the amplitude of oxytocin-induced contractions by formoterol was antagonized with ICI 118.551 (10(-6) M), but they were not changed by metoprolol (10(-6) M) or SR 59230A (10(-6) M). The inhibition of the amplitude of oxytocin-induced contractions by BRL 37344 were antagonized with SR 59230A (10(-6) M), but they were not changed by metoprolol (10(-6) M) or ICI 118.551 (10(-6) M). Formoterol and BRL 37344 increased cAMP levels. BRL 37344 increased cGMP levels in BRL 37344 group more than control group, but this increase is less significant than cAMP levels (P>0.05). Formoterol and BRL 37344 decreased amplitude of myometrial contractions with similar potency, but efficacy of formoterol was better than BRL 37344.

Anticachectic effects of formoterol: a drug for potential treatment of muscle wasting

In cancer cachexia both cardiac and skeletal muscle suffer an important protein mobilization as a result of increased proteolysis. Administration of the beta2-agonist formoterol to both rats and mice bearing highly cachectic tumors resulted in an important reversal of the muscle-wasting process. The anti-wasting effects of the drug were based on both an activation of the rate of protein synthesis and an inhibition of the rate of muscle proteolysis. Northern blot analysis revealed that formoterol treatment resulted in a decrease in the mRNA content of ubiquitin and proteasome subunits in gastrocnemius muscles; this, together with the decreased proteasome activity observed, suggest that the main anti-proteolytic action of the drug may be based on an inhibition of the ATP-ubiquitin-dependent proteolytic system. Interestingly, the beta2-agonist was also able to diminish the increased rate of muscle apoptosis (measured as DNA laddering as well as caspase-3 activity) present in tumor-bearing animals. The present results indicate that formoterol exerted a selective, powerful protective action on heart and skeletal muscle by antagonizing the enhanced protein degradation that characterizes cancer cachexia, and it could be revealed as a potential therapeutic tool in pathologic states wherein muscle protein hypercatabolism is a critical feature such as cancer cachexia or other wasting diseases.

Tocolytic effects of formoterol are associated with local change in the progesterone/estradiol ratio

OBJECTIVE

The aim of the study was to determine whether a beta(2)-adrenoceptor agonist, formoterol, inhibits premature delivery in connection with change in estradiol and progesterone concentrations in the amniotic fluid in ovariectomized rats.

STUDY DESIGN

Pregnant rats at the 15th day of gestation were bilaterally ovariectomized and given injection of 17beta-estradiol immediately after the operation and every 24 h. An osmotic pump filled with a solution of formoterol or saline was also implanted subcutaneously into the back of each. The animals were killed by decapitation under light ether anesthesia 18, 36, 54 or 72 h after ovariectomy, and the numbers of undelivered fetuses and newborn were counted. Amniotic fluid was collected 16, 36, and 54 h after ovariectomy.

RESULTS

Formoterol (0.15 mg/(kg h)) reversed the decline in premature delivered fetuses due to 17beta-estradiol 54 and 72 h after ovariectomy. Although no influence was evident regarding the progesterone and estradiol concentrations in amniotic fluid in ovariectomized rats supplemented with 17beta-estradiol, formoterol significantly inhibited the increment in the estradiol/progesterone ratio as well as the elevation in prostaglandin F2alpha concentration.

CONCLUSION

These findings indicate that tocolytic effects of formoterol may be associated with suppression of uterine activity due to modulation of hormone secretion.

Tocolytic activity of formoterol against premature delivery in mice

The tocolytic activity of formoterol (eformoterol), a long-acting potent beta(2)-adrenoceptor agonist, was assessed in pregnant mice, with determination of uterine effects on the 15th and 16th days of gestation. For examination in the lipopolysaccharide-induced premature delivery model, osmotic pumps filled with formoterol or saline solution were implanted subcutaneously under the back skin. The mice were sacrificed 18-20 h thereafter, and the numbers of fetuses in the uteri and the newborn were counted. The uteri, amniotic membranes and placenta were also rapidly removed for determination of IL-6 concentrations. Furthermore, the effect of formoterol on IL-6 secretion from mouse amnion cells was determined. Formoterol and ritodrine inhibited contraction responses of isolated mouse uteri and their intravenous administration resulted in lowered uterine motility. Lipopolysaccharide (30 microg mL(-1)/mouse) induced premature delivery, attributable to increased IL-6 secretion, and formoterol suppressed this. Doses of 5-500 microg/mouse thus reduced the number of prematurely delivered newborn, and 50 microg/mouse also depressed IL-6 secretion. On histopathologic analysis, the marked oedema and slight haemorrhage in the mouse cervix induced by lipopolysaccharide were reduced by administration of the beta(2)-adrenoceptor agonist. Neither formoterol (10(-7)-10(-5) M) nor ritodrine (10(-7)-10(-5) M) influenced spontaneous secretion of IL-6 in amnion cells. However, at 10(-7) and 10(-5) M, and 10(-6) and 10(-5) M, respectively, they inhibited lipopolysaccharide-induced IL-6 secretion and this inhibitory effect was competitively reversed by addition of ICI-118,551 (beta(2)-adrenoceptor antagonist), but not atenolol (beta(1)-adrenoceptor antagonist). These findings strongly suggest that formoterol can suppress premature delivery mediated by its actions on IL-6 secretion.