Fig 1.
The effects of CaCl2 on KCl-induced (40 mM) uterine contractions at concentrations range 3-120 mM in a cumulative manner.
Contractions were induced in the uterine rings prepared from non-pregnant and 22nd day pregnant rats. (A) a representative record for non-pregnant uterine tissue and (B) a 22nd day pregnant rat tissue.
Fig 2.
The schematic diagram of the in vivo investigation of the uterine action of T in non-pregnant and 22nd day pregnant anesthetized rats.
T was administered in different doses (3, 10, 30, 100 or 300 mg/kg ip) alone and with flutamide (100 mg/kg ip) using strain gauge sensors, AUC was obtained, and the percent of relaxation was calculated and analyzed.
Fig 3.
The in vivo effect of solvent on the contraction of the rat uterine muscle (n = 7-8 per group).
A and B are representative records of uterine contractions with strain gauge sensors, C and D represent the solvent effect in non-pregnant (A, C) and 22nd day pregnant rats (B, D). Data are expressed as relaxation percent, First admin.: first administration of solvent, Second admin.: second administration of solvent dose.
Fig 4.
The effect of time passage on the contraction of the rat uterine muscle in vivo (n = 7-8 per group).
A and B are representative records of uterine contractions with strain gauge, C and D represent the fatigue test in non-pregnant (A, C) and 22nd day pregnant rats (B, D), respectively. Data are expressed as percent relaxation.
Table 1.
Pharmacokinetic parameters of T after single ip injection of 10 mg/kg dose in non-pregnant and 22nd day pregnant rats (n = 5 per group). Data were analysed using an unpaired t-test and are expressed as mean and SD.
Fig 5.
Plasma T concentration-time curves after a single ip injection (10 mg/kg) in non-pregnant and 22nd day pregnant rats (n = 5 per group).
Data are expressed as mean ±SD (ng/ml). *: p < 0.05, **: p < 0.01, ns: non-significant compared to the non-pregnant value.
Fig 6.
Plasma T levels before and 30 min after the single dose of T administration in non-pregnant and 22nd day pregnant rats (n = 4-8 per group).
The data were analyzed using ANOVA-Dunnett’s multiple comparison test compared to the control values within the group and are expressed as mean ± SD. ns: non-significant, **: p < 0.01 **** p < 0.0001, NP; non-pregnant, P; 22nd day pregnant, T; testosterone, (3, 10, 30, 100, 300 mg/kg ip).
Fig 7.
The inhibitory effect of T and nifedipine on non-pregnant and 22nd day pregnant uterine tissues in vitro (n = 4-8).
The contractions were initiated with KCl (40 mM) in a Ca2+-free buffer. Cumulative administration of CaCl2 launched uterine contractions that were completely blocked by T and nifedipine. Data were analyzed using non-linear regression and are expressed as percent of contraction mean ± SD, CaCl2: calcium chloride, T: testosterone, Ni: nifedipine.
Table 2.
Emax and ED50 values of the uterine relaxing dose-response curves of T in non-pregnant and 22nd day pregnant rats. (n = 5-8 per group).
Fig 8.
The non-genomic uterine relaxing effect of T in vivo.
A, C, and B, D are representative records of strain gauge-detected uterine contractions in non-pregnant and 22nd day pregnant rats, respectively. T (ip) induced a dose-dependent but flutamide-resistant uterine relaxing effect in non-pregnant (E) and late pregnant (F) rats. Each point is the result of a single dose of T or T+flutamide, n = 5-8 per group; the data are expressed as relaxation % mean ± SD.
Fig 9.
Plasma levels of 4-HPPD after T administration (n = 6-8 per group).
Plasma levels of 4-HPPD were measured before and 30-minutes after the administration of T doses (100 or 300 mg/kg ip) for non-pregnant and 22nd day pregnant rats. ****; p < 0.0001, ns; non-significant, NP; non-pregnant, P; 22nd day pregnant, T100: testosterone 100 mg/kg; T300: testosterone 300 mg/kg. Data were analyzed using ANOVA-Dunnett’s multiple comparison test and are expressed as mean ± SD.
Fig 10.
Schematic diagram summarizing the effect of T on inhibiting uterine contraction.
The red line represents the inhibition demonstrated in our experiment, while the blue (inhibition) and green (activation) lines represent the mechanisms described in previous studies. T inhibits voltage dependent Ca2+-channels having a crucial role in its uterine relaxing effect (red line). Furtherly, T stimulates the 7TM (G-protein coupled) receptors (short green arrow) and increases cAMP level of the uterine tissues which inhibits the Ca2+channels activity (blue line) [34]. Additionally, T activates different K+ channel types in smooth muscle (long green arrow), that also leads to relaxation by reducing intracellular K+ level [35]. AC: Adenylyl cyclase, ATP: adenosine triphosphate, cAMP: cyclic adenosine monophosphate, T: testosterone, 7TM: seven-transmembrane receptor (G-protein coupled receptor)”.