0000000000338033
AUTHOR
Julio D. Martín
Effects of Mn2+ on the responses induced by different spasmogens in the oestrogen-primed rat uterus
Abstract We investigated the effect of Mn 2+ on the mechanical responses evoked by high K + (60 mM) or low Na + (25 mM) solutions, oxytocin and neurokinin A in the oestrogen-primed rat uterus. In a Ca 2+ -free, Mn 2+ (0.54 mM)-containing solution, high K + or low Na + solutions produced contractions of smaller amplitude than those observed in a normal Ca 2+ (0.54 mM) solution, which were abolished by nifedipine (1 μM). Oxytocin (1 μM) and neurokinin A (1 μM, in the presence of phosphoramidon 1 μM) evoked nifedipine-insensitive contractile responses similar to (oxytocin) or smaller (neurokinin A) in amplitude than those observed in Ca 2+ (0.54 mM)-containing solution. In strips loaded with C…
Characterization of tachykinin receptors in the uterus of the oestrogen-primed rat
The aim of our study was to characterize the tachykinin receptor population in the oestrogen-primed rat uterus. For this purpose, we investigated the receptor type(s) responsible for tachykinin-induced contraction of longitudinally-arranged smooth muscle layer. The effects of substance P (SP), neurokinin A (NKA), neurokinin B (NKB) and several of their analogues with well-defined selectivities for tachykinin NK1, NK2 and NK3 receptors were studied and their inhibition by the selective nonpeptide tachykinin receptor antagonists (S)1-(2-[3-(3,4-dichlorophenyl)-1-(3-isopropoxyphenylacetyl)piperidin-3-yl]ethyl)-4-phenyl-1-azoniabicyclo[2.2.2]octane chloride (SR 140333, NK1-selective), (S)-N-met…
Influence of calcium on the effects of okadaic acid and its interaction with caffeine and theophylline in rat myometrium.
The effects of okadaic acid (OA), a monocarboxylic acid produced by marine dinoflagellates belonging to the genera Dinophysis and Prorocentrum, and their interactions with theophylline and caffeine were studied on the rat-isolated uterus in a calcium-containing medium and a calcium-free medium in the presence of 10−3 M EGTA. Okadaic acid (5 × 10−6 to 5 × 10−5 M) induced a concentration-dependent contraction of the rat-isolated uterus corresponding, with 5 × 10−5M, to 142.3±6.1% (n = 7) of the contraction induced by oxytocin 10−6 M. The time to peak tension was inversely proportional to the maximum effect produced. The contraction was not sustained and was followed by a concentration-depende…
Regulation by oestrogens of tachykinin NK3 receptor expression in the rat uterus.
The expression of the tachykinin NK3 receptor and its regulation by ovarian steroids were analyzed by reverse transcription-polymerase chain reaction (RT-PCR) in uteri from ovariectomized rats. A single transcript corresponding to the 325-bp product expected for the tachykinin NK3 receptor was detected in uteri from olive oil-treated (control) ovariectomized rats. The level of tachykinin NK3 receptor mRNA in progesterone-treated animals was similar to that observed in uteri from control ones. Tachykinin NK3 receptor mRNA levels were significantly smaller in uteri from oestrogen-treated ovariectomized rats, with approximately a 32-fold decrease. These findings suggest that oestrogen, but not…
Changes in the Expression of Tachykinin Receptors in the Rat Uterus During the Course of Pregnancy1
In the mammalian female reproductive tract, tachykinin neuropeptides, such as substance P (SP), are localized to a population of sensory fibers and their precise physiological role is still unknown. The aim of the present study was to characterize the population of tachykinin receptors in the pregnant rat uterus and to assess their regulation during the course of pregnancy and after delivery. The expression of the tachykinin NK(1) receptor (NK(1)R), the tachykinin NK(2) receptor (NK(2)R), and the tachykinin NK(3) receptor (NK(3)R) in uteri from rats at different stages of pregnancy and on Day 1 postpartum was investigated by using a semiquantitative reverse transcription-polymerase chain re…
Effect of inhibition of the electrogenic Na+/K+ pump on the mechanical activity in the rat uterus.
The effects of ouabain and K(+)-free solution were studied in estrogen-primed rat uterine strips under resting tone or repeatedly stimulated with KCl, acetylcholine or oxytocin applied for 20 minutes at 60 minute intervals. These effects were compared with those of the K+ channel opener cromakalim. In preparations under resting tone, ouabain (0.1 mM and 0.3 mM) induced rhythmic contractions which disappeared after 20-30 minutes whereas at a higher concentration (1 mM) it evoked a rapid, phasic response followed by a small tonic contraction. Exposure of the strip to a K(+)-free solution induced either rhythmic waves, which ceased after 8-10 minutes, or a single phasic contraction which was f…
Inhibitory effects of okadaic acid on rat uterine contractile responses to different spasmogens
In the present study, we examined the effects of okadaic acid, a selective inhibitor of type I and 2A protein phosphatases, on the mechanical responses evoked by oxytocin, K + - and Na + -modified solutions and ouabain in estrogen-primed rat myometrium. Oxytocin elicited a rapid, phasic contraction followed by rhythmic oscillations. The phasic response was partially resistant to the absence of external Ca 2+ . Okadaic acid (1 μM) and the L-type calcium channel blocker nifedipine (1 μM) abolished the oscillatory component and reduced the initial, phasic response to about 80% of the control response. High K + (60 mM) solution, ouabain (1 mM), K + -free medium and low Na + (25 mM) solution ind…