The objective of this work was to examine the smooth muscle relaxing properties of antioquine, compared to papaverine, in isolated rat uterus. The results obtained show that both antioquine and papaverine are capable of relaxing sustained contractions induced by Ca2+ in K-depolarizing solution as well as the spontaneous activity of rat uterus. Antioquine (0.1 mM, 0.5 mM and 1 mM) also induces a displacement to the right of the dose-response curves to Ca2+, and the antagonism was not competitive. Papaverine produced a decrease in the frequency and amplitude of contractile responses induced by oxytocin, and these inhibitory effects were observed regardless of whether papaverine was added before or after the induced contractions. On the other hand, antioquine only modified the frequency of contractile responses to oxytocin or desynchronized cumulative dose-response curves to oxytocin when the uterus was preincubated with this alkaloid before addition of the agonist. These experiments suggest that the relaxant effects produced by antioquine may be due to the blockade of calcium movements across the cell membrane, mainly through voltage-operated channels, whereas papaverine affects Ca2+-entry both through VOCs and through ROCs.

Alkaloids↗

PubMedDate not supplied

Study of the strontium response in isolated rat aorta.

We have studied the effects of the cumulative application of Sr2+ in isolated rat aorta in a normal and in a Ca2+-free solution containing EDTA 1 mM. Sr2+ induced a concentration-dependent contraction which was reduced by verapamil (5 X 10(-6) and 10(-7) M) and lanthanum (1 and 2 mM). Sr2+ also induced a contraction in K+-depolarized medium. In aorta strips depleted of Ca2+ by several applications of noradrenaline (10(-6) M), Sr2+ induced a dose-response contraction in a Ca2+-free solution. These findings suggest that the influx of external Ca2+ is only partly responsible for the Sr2+-induced contraction and that another intracellular mechanism is involved in the response.

Animals↗

PubMedDate not supplied

Incubated or superfused rat lung parenchymal strip: a valid preparation for direct measurement of beta-responses.

Responses to the beta-adrenoceptor agonists isoprenaline (Iso) (non selective), salbutamol (Sal) (beta 2-selective) and noradrenaline (NA) (beta 1-selective) were studied on incubated and superfused rat lung strip. In both conditions, Iso and Sal elicited dose-related relaxations of lung strip and these responses were unaffected by the presence of phentolamine (Phen) 10(-5) M. Contractile responses to NA were obtained when it was used alone whereas in the presence of Phen 10(-5) M, NA elicited relaxant responses. The relative potencies of Iso : Sal : NA (plus Phen) were 100 : 20 : 0.69. This demonstrates that beta 2-adrenoceptor is the predominant beta-subtype involved in responses. Propranolol (10(-4) M) completely abolished the relaxant responses to Iso. However, after the addition of Iso tissue responded normally to drugs acting by other mechanisms. Thus, relaxations were obtained with caffeine and contractions with acetylcholine (AcH) or NA. This shows that responses to Iso are mediated only by beta-adrenoceptors. Propranolol and the selective beta-blocking agents butoxamine (beta 2) and atenolol (beta 1) competitively antagonized the effects of Iso. The Schild plots obtained had slopes which did not differ significantly from -1 and mean pA2 values were: 7.82 for propranolol; 6.32 for butoxamine and 5.22 for atenolol. These experiments were carried out in the absence of catecholamine uptake inhibitors, since in a preliminary set of experiments no significant changes of lung strip responses to Iso were observed in the presence of cocaine (10(-5) M) or corticosterone (10(-5) M). In conclusion, it appears that incubated rat lung strip possesses intrinsic tone and, although it cannot be considered a representative preparation of peripheral airways, it provides a valid model for investigating the direct-effects of drugs which act at beta-adrenoceptors.

Albuterol↗

PubMedDate not supplied

Role of intracellular calcium stores in the contractile response of uterus to several agonists.

A comparison was made of contractions produced by submaximal doses of oxytocin, noradrenaline, PGE2 and PGF2 alpha in estrogen-dominated rat uterus after the preparation had been loaded in Ca-free medium supplemented with EDTA 3 mM. The experiments were carried out in the presence of EDTA 1 mM to complex the contaminating Ca. The contraction was sustained as long as the preparation was exposed to the drug and was relaxed by washing. Cumulative concentration-response curves to oxytocin (6.25-100 microM), noradrenaline (0.05-1.6 mM), PGE2 (0.1-1.6 microM) and PGF2 alpha (0.02-0.32 microM) were made. The threshold concentration for PGF2 alpha was much lower than for PGE2, oxytocin and noradrenaline. Isoprenaline (10- -10(-4)M), KCl (56.3 mM) and caffeine (5 mM) were added. The results showed that isoprenaline and KCl did not produce contractile response. Caffeine produces only a small decrease in the resting tension and this effect is not reversible. After addition of noradrenaline, a concentration of oxytocin (6 microM) produced a uterine contraction smaller than the control response of uterus to oxytocin. The response to the oxytocin applied after washing out the caffeine was the same as the control response. All agonists tested that were capable of inducing uterine contraction in Ca-free medium act through specific receptors. This suggests a relation between receptor-operated Ca-channels and intracellular Ca-stores.

Animals↗

PubMedDate not supplied

[Role of intracellular Ca in the relaxant action exerted by sulfonylureas on uterine smooth muscle].

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Animals↗

PubMedDate not supplied

Different actions of some relaxant agents acting via the cAMP system in rat uterus.

The influence of propranolol, isoprenaline, papaverine and caffeine on basal tone and contractile responses to spasmogens (oxytocin, KCl) was investigated in the presence and the absence of external calcium in estrogen-treated rat uterus. Isoprenaline, papaverine and caffeine relaxed precontracted uterus and caffeine also decreased the basal tone of uterine muscle in calcium-containing or calcium-free solution. Propranolol had a dual activity in calcium-free medium: lower concentrations contracted the sustained contraction elicited by oxytocin, whereas the highest concentration partially relaxed it. In calcium-containing solution the highest dose of propranolol partially inhibited KCl-induced contractions.

Animals↗

PubMedDate not supplied

[Reflexions on the aspects characterizing the new INAIL tables regarding occupational diseases].

The AA examine the new Tables for occupational diseases in industry and agriculture, which have recently approved with the Presidential Decree n.336, april 13, 1994. The main innovations are analysed, like the elimination of some too generic terms, which had often allowed contrasting interpretations and a non univocal jurisprudence. Other innovative aspects regard the new acquisitions of occupational medicine and strengthen, in the new formulation, the principles of the presumption of law in establishing a relation of cause and effect.

Deafness↗

PubMedDate not supplied

[D.lgsl. 625/1994--Protection against carcinogenic agents: the obligation to educate].

According to act 626/1994, employers have the duty to inform and train workers and their representatives. The implementation of training activities requires the following points: planning the training program according to the needs of the target population, use of the methods aimed at promoting learning and the adoption of safe behaviour, setting-up of evaluation tools. The disciplines of risk perception and communication and adult training may provide useful contribution in this frame. At the light of the preliminary experiences in this field, the importance of the following items for workers, workers representatives and employers is emphasized: probabilistic causality models, role of cognitive and emotional factors in the learning process, definition of carcinogenic according to national and international organisation, meaning of TLV with respect to carcinogenic exposure, interaction between carcinogens in the case of multiple exposition, risk evaluation, preventive measures, transfer of carcinogen risk from workplace to domestic environment, due to lack of compliance with basic hygienic rules such proper use of work clothes.

Adult↗