Prompt effect of progesterone on the adrenergic response of smooth muscles

Semen collection by urethral catheterization and electro-ejaculation with different voltages, and the effect of holding temperature and cooling rate before cryopreservation on semen quality in the Japanese macaque (Macaca fuscata)

In the Japanese macaque, semen has been collected by electro-ejaculation (EE), using the higher voltage stimuli compared to other species including genus Macaca. Semen coagulate immediately after ejaculation, which makes difficult to produce high-quality semen for artificial insemination. Recently, semen collection using urethral catheterization (UC) has been reported in carnivore and this technique may allow semen collection without coagulation in a less invasive manner. Further, the temporal preservation temperature and cooling rate of semen during cryopreservation affect post thawing sperm quality. In this study, to improve semen quality and quantity, as well as the animal welfare, semen collection was performed by EE with high (5-15 V) or low (3-6 V) voltage, UC and a combination of the two (EE-UC). It has been suggested that a high voltage is necessary for semen collection, but 10 V stimulation was effective enough and 15 V is for additional sperm collection. Also, liquid semen was collected by EE-UC and this could increase the total number of sperm. Further, to improve the post thawing sperm motility, semen was kept at four temperatures (4, 15, 25 and 37˚C) for 60 min, and processed with two cooling procedures (slow cooling before second dilution and fast cooling after second dilution). Holding semen at 25˚C and fast cooling after the second dilution maintained progressive motile sperm rate. The present results will contribute to the improvement of semen collection and animal welfare of Japanese macaques.

Calcium channel blockers as tocolytics: principles of their actions, adverse effects and therapeutic combinations

Dihydropyridine Ca²⁺ channel blockers (CCBs) are widely accepted in the treatment of premature labour. Their mechanism of action in tocolysis involves the blockade of L-type Ca²⁺ channels, influenced by the Ca²⁺-activated K⁺ channels, beta-adrenergic receptors (β-ARs) and sexual hormones. In clinical practice, most experience has been gained with the use of nifedipine, whose efficacy is superior or comparable to those of β-agonists and oxytocin antagonists. Additionally, it has a favourable adverse effect profile as compared with the majority of other tocolytics. The most frequent and well-tolerated side-effects of CCBs are tachycardia, headache and hypotension. In tocolytic therapy efforts are currently being made to find combinations of tocolytic agents that yield better therapeutic action. The available human and animal studies suggest that the combination of CCBs with β-AR agonists is beneficial, although such combinations can pose risk of pulmonary oedema in multiple pregnancies and maternal cardiovascular diseases. Preclinical data indicate the potential benefit of combinations of CCBs and oxytocin antagonists. However, the combinations of CCBs with progesterone or cyclooxygenase inhibitors may decrease their efficacy. The CCBs are likely to remain one of the most important groups of drugs for the rapid inhibition of premature uterine contractions. Their significance may be magnified by further clinical studies on their combined use for tocolysis.

Absence of mitochondrial progesterone receptor polymorphisms in women with spontaneous preterm birth

OBJECTIVE

The truncated mitochondrial progesterone receptor (PR-M) is homologous to nuclear PRs with the exception of an amino terminus hydrophobic membrane localization sequence, which localizes PR-M to mitochondria. Given the matrilineal inheritance of both spontaneous preterm birth (SPTB) and the mitochondrial genome, we hypothesized that (a) PR-M is polymorphic and (b) PR-M localization sequence polymorphisms could result in variable progesterone-mitochondrial effects and variable responsiveness to progesterone prophylaxis.

METHODS

Secondary analysis of DNA from women enrolled in a multicenter, prospective, study of 17 alpha-hydroxyprogesterone caproate (17OHPC) versus placebo for the prevention of recurrent SPTB. DNA was extracted from stored saliva.

RESULTS

The PR-M localization sequence was sequenced on 344 patients. Sequences were compared with the previously published 48 base-pair sequence, and all were identical.

CONCLUSIONS

We did not detect genetic variation in the mitochondrial localization sequence of the truncated PR-M in a group of women at high risk for SPTB.

Membrane-bound progesterone receptor expression in human aortic endothelial cells

Observational studies demonstrate that estradiol and progesterone affect vasoreactivity. In animal studies, progesterone treatment causes immediate relaxation of precontracted arteries with inhibition of calcium influx in vascular endothelial and smooth muscle cells, suggesting a non-genomic mechanism of action. In this study we investigated the presence of novel membrane-bound progesterone receptors in human aortic endothelial cells and correlated the expression with cell-cycle stage. Western blotting analysis with an antibody directed to the hormone-binding domain of the classic progesterone receptors shows predominant bands at 100 and 60 kD, whereas analysis with an antibody to the DNA-binding region shows only the 100-kD band. In contrast, classic nuclear progesterone receptors B and A are identified at 116 and 94 kD in similarly processed T47D cells. Both novel bands localize to the membrane fraction after differential centrifugation. Plasma membrane-bound progesterone receptor was further shown with immunofluorescent antibody and ligand-binding studies in a small percentage of human aortic endothelial cells. Fluorescent activated cell sorting demonstrated that approximately 8% of the human aortic endothelial cells expressed a plasma membrane progesterone receptor and that a greater percentage of the expressing cells were in the G2/M-phase of the cell cycle. Treatment with progesterone conjugated to BSA did not show any significant cell-cycle changes. Plasma membrane-bound progesterone receptor in vascular endothelial cells may regulate the non-genomic actions of progesterone, and expression of the receptor appears to vary with cell cycle stage.

Cloning and expression of a novel, truncated, progesterone receptor

Progesterone acts via two specific receptors to affect gene transcription in target tissues. Progesterone receptor (PR) B contains 933 amino acids while PR A is a truncated version lacking the initial 164 amino acids. We have cloned a novel, truncated PR from both human adipose and aortic cDNA libraries. This cDNA encodes a predicted protein of 314 amino acids, termed PR-M. Initiation of transcription of PR-M occurs in intron 3, with the initial exon identical to exon 4 of the genomic PRs, except for a novel 16 amino acid amino-terminal sequence, consistent with a signal peptide. The remainder of PR-M is identical to the genomic PR. Transcript for this protein was identified by RT-PCR in human aortic endothelial cells and T47D breast cancer cells. Expression of PR-M in Sf 9 insect cells results in a 38-kDa protein, demonstrated in human aortic endothelial cells and T47D breast cancer cells. The function of PR-M remains to be determined. The presence of a signal peptide and the lack of a DNA binding region suggests a non-genomic action.

The effect of progesterone on spontaneous and agonist-evoked contractions of the rat aorta and portal vein

The mechanisms underlying the suppression of vasocontractility caused by progesterone were investigated by studying changes in the contractile force of rat isolated aorta and portal vein, induced by altering extracellular concentrations of noradrenaline (NA) potassium ions (K+) and calcium ions (Ca2+). In the aorta, progesterone (10 microM) had a general suppressive effect on NA-, Ca2+- and K+-induced contractions. In contrast, in the portal vein a more selective suppression of contractions was observed. Both tonic and phasic components of contractions induced by cumulative addition of Ca2+ to tissues equilibrated in Ca2+-free saline were suppressed. The phasic but not tonic components of contractions induced by NA addition were suppressed. There was no significant effect on tonic contractions induced by elevated (40-120 mM) K+, but a concentration-dependent suppression of the phasic component of contractions was observed during depolarisation with smaller elevations of K+ concentrations (5-20 mM). These results suggest that on the portal vein the suppressive effect of progesterone is due to a potassium channel opening action, whilst on the aorta a different or additional mechanism of suppression exists.