Effect of progesterone on norepinephrine release from mouse adrenergic terminals in vitro

Calcium and depolarization-dependent effect of pregnenolone derivatives on uterine smooth muscle

1. The effects of several gestagens (pregnenolone [1 to 30 microM], 20 alpha-hydroxy-pregnenolone [1 to 30 microM], and 20 beta-hydroxypregnenolone [1 to 30 micro M]) on rat uterine contraction induced by KCl (60 mM) and CaCl2 (30 microM to 6 mM) have been assayed. 2. The three drugs relaxed the tonic contraction induced by KCl in a concentration-dependent way. The respective EC50 values were: 27.6 +/- 1.58 microM (pregnenolone), 4.1 +/- 0.12 microM (20 alpha-hydroxy-pregnenolone), and 11.2 +/- 1.04 microM (20 beta-hydroxypregnenolone). CaCl2 (1 to 10 mM) totally counteracted the relaxing effect of pregnenolone but only partially compared to that of 20 alpha- or 20 beta-hydroxy-pregnenolone. 3. CaCl2 (30 microM to 6 mM) produced concentration-dependent contraction of rat uterus in medium lacking calcium plus 30, 60, or 90 mM of KCl. The EC50 values of CaCl2 were: 0.38 +/- 0.072, 0.183 +/- 0.015, and 0.183 +/- 0.015 mM in a medium with 30, 60, or 90 mM of KCl, respectively. 4. Pregnenolone (10 microM) did not significantly modify the EC50 of CaCl2 in a medium with 30, 60, or 90 mM of KCl. However, 20 beta-hydroxypregnenolone (10 microM) antagonized, in a noncompetitive manner, the concentration-response curve to CaCl2. 5. 20 alpha-Hydroxypregnenolone (4 microM) antagonized the concentration-response curve to CaCl2 in a competitive manner. This antagonism was directly related to the concentration of KCl in the medium. 6. Our results suggest a different calcium antagonist effect of the three gestagens assayed.

Influence of hormonal status in relaxant effect of diethylstilbestrol and nifedipine on isolated rat uterus contraction

1. The effects of diethylstilbestrol (DES, 10(-7)-10(-5) M) and nifedipine (10(-10)-10(-7) M) on KCl (60 mM)-induced tonic contraction in the uterus of ovariectomized and 17 beta-estradiol (0.1 mg/kg/day, s.c.)-, 17 alpha-estradiol (0.1 mg/kg/day, s.c.)-, or progesterone (2 mg/kg/day, s.c.)-treated rats have been assayed. 2. The dose-dependent relaxation produced by nifedipine in ovariectomized rats (EC50 = 5.59 +/- 1.25 x 10(-9) M) is potentiated in uterus of rats treated with 17 beta-estradiol and progesterone (EC50 = 0.59 +/- 0.1 and 0.49 +/- 0.1 x 10(-9) M, respectively) but not in the 17 alpha-estradiol-treated rats (3.01 +/- 0.6 x 10(-9) M). 3. The relaxation produced by DES on ovariectomized rats (EC50 = 0.84 +/- 0.14 x 10(-6) M) is reduced when the rats are treated with 17 beta-estradiol (EC50 = 2.22 +/- 0.2 x 10(-6)M) or progesterone (EC50 = 1.24 +/- 0.08 x 10(-6) M), but unmodified by 17 alpha-estradiol (EC50 = 0.58 +/- 0.01 x 10(-6) M). 4. The nifedipine-induced relaxation is reversed with Bay K 8644 (10(-10)-10(-6) M) in all experimental conditions. However, Bay K 8644 counteracted the relaxation of DES at 45.7% on ovariectomized rats but this was lower than 30% in the other groups. 5. Our results suggest that in ovariectomized rats the effects of both nifedipine and DES are similar, but 17 beta-estradiol and progesterone produce a contrary effect on the relaxation induced by nifedipine and DES (by increasing the nifedipine and decreasing the DES effects).(ABSTRACT TRUNCATED AT 250 WORDS)

Progesterone and pregnanolone derivatives relaxing effect on smooth muscle

1. The effect of gestagens, 5 alpha-hydroxyprogesterone (10(-6) x 10(-5) M), 5 beta-hydroxyprogesterone (10(-6)-3 x 10(-5) M), progesterone (6 x 10(-6)-10(-4) M), pregnanolone (10(-6)-10(-5) M), allopregnanolone (10(-6)-10(-4) M) and epipregnanolone (10(-6)-6 x 10(-5) M) on rat uterine contractions induced by KCl (60 mM), has been assayed. 2. All drugs assayed relaxed the tonic-contraction induced by KCl in a concentration-dependent way. The respectives IC50 were 31.3 +/- 4.1 x 10(-6) M (progesterone), 8.9 +/- 0.8 x 10(-6) M (5 alpha-hydroxyprogesterone), 3.8 +/- 0.3 x 10(-6) M (5 beta-hydroxyprogesterone), 3.1 +/- 0.1 x 10(-6) M (pregnanolone), 21.2 +/- 3.1 x 10(-6) M (allopregnanolone) and 6.3 +/- 1.3 x 10(-6) M (epipregnanolone). This relaxing effect was partially or totally counteracted by CaCl2 (1-10 mM) 3. Cycloheximide (10 micrograms/ml) significantly shifted to the right the effect of allopregnanolone but not the effect of the other drugs. Actinomycin D (5 micrograms/ml) did not modify the effect of allopregnanolone. 4. Our results suggest that the relaxing effect of gestagens in the rat uterus could be related to inhibition on calcium influx and mainly occur through non-genomic mechanisms.

Effects of androgens on isolated rat uterus

The 5 alpha- and 5 beta-dihydrotestosterone (DHT) androgens relax KCl-induced tonic contraction in rat uterus, in a dose-dependent way. The 5 alpha and 5 beta-DHT relaxing effect is counteracted by CaCl2 (0.1-10 mM). The 5 alpha-DHT, but not the 5 beta-DHT, effect was reduced by cycloheximide (10 micrograms/ml) and by actinomycin D (5 micrograms/ml). Flutamide at 10(-6) M shifted the effect of 5 alpha-DHT to the right. However, other doses of flutamide or cyproterone acetate did not modify the effect of both androgens. We suggest a non-genomic effect of 5 alpha-DHT and 5 beta-DHT in rat uterus contraction but that intracellular and genomic actions play a part in the relaxing effect of 5 alpha-DHT.

Mast cells mediators evoke contractility and potentiate each other in mouse uterine horns

1. The ability of prostaglandin F2 alpha (PGF2 alpha), histamine and serotonin to induce and/or potentiate contractions in mouse uterine horns was studied in an attempt to analyze whether uterine mast cells degranulation could favor contractions during labor. 2. PGF2 alpha was the most potent of the three compounds (EC50 = 0.7 microM), being followed by serotonin (EC50 = 1.2 microM) and histamine. Between 10 and 100 microM histamine only evoked weak contractions, not higher than 50% of maximal amplitude of contractions. 3. Serotonin (0.1 microM) potentiated the contractile effect of both histamine and PGF2 alpha when added simultaneously with the corresponding compound to the isolated organ bath. Also, histamine at threshold contractile concentration (3 microM) was able to potentiate the contractile effect of both serotonin and PGF2 alpha. 4. The potentiating effect of PGF2 alpha on both histamine and serotonin evoked contractions was recorded after treating the preparation with 10 microM of the compound for at least 10 min before the corresponding concentration-effect curves were performed. 5. It is postulated that the simultaneous presence of these mast cells mediators in myometrium could be an important stimulus for both to trigger and/or to maintain contractions during labor.

Effects of antiandrogens and progesterone on isolated rat uterus

1. The effect of progesterone (P, 6 x 10(-6)-6 x 10(-5) M) and the antiandrogens cyproterone acetate (CPA, 10(-7)-10(-5) M), flutamide (F, 10(-6)-6 x 10(-5) M) and spironolactone (S, 10(-6)-6 x 10(-5) M) on the KCl-induced tonic contraction of the isolated rat uterus have been assayed. 2. The antiandrogens relaxed, in a dose-dependent way, the KCl-induced contraction (EC50, 2.804 +/- 0.506 x 10(-6); 1.671 +/- 0.308 x 10(-5); and 3.042 +/- 0.14 x 10(-5) M, respectively for CPA, S and F). P also relaxed the KCl-induced contraction (EC50, 2.436 +/- 0.524 x 10(-5) M). 3. CaCl2 (0.1-10 mM) counteracted the relaxing effect of CPA, S, F, and P, respectively, up to 100, 80.63, 60.66 and 90.57%. 4. The 17-OH-progesterone derivative CPA, but not S or F, reduces at small doses (6 x 10(-8) M), but not at higher concentrations (6 x 10(-7)-6 x 10(-6) M), the relaxing effect of progesterone.

Nicotine stimulates adrenergic terminals and inhibits contractions of mouse uterine horns

1. Nicotine (1-100 microM) stimulated both basal and electrically evoked release of 3H-norepinephrine and also caused a transient inhibition of contractions in an in vitro preparation of mouse uterine horns. 2. The inhibitory effect of nicotine on electrically evoked contractions was potentiated by aminophylline (89 micrograms/ml), and overcome by both propranolol (1 microM) and by omitting magnesium from the physiological solution. Acetylcholine (10 microM), in the presence of atropine (10 microM) was able to reproduce the inhibitory effect of nicotine. 3. These pharmacological findings suggest that the inhibitory action of nicotine on electrically evoked contractions in mouse uterus could be indirect, i.e. mediated through the action of this compound on presynaptic nicotine receptors located on adrenergic terminals.