The effect of pregnenolone sulfate on uterine contractility

Transient receptor potential M3 channels are ionotropic steroid receptors in pancreatic beta cells

Transient receptor potential (TRP) cation channels are renowned for their ability to sense diverse chemical stimuli. Still, for many members of this large and heterogeneous protein family it is unclear how their activity is regulated and whether they are influenced by endogenous substances. On the other hand, steroidal compounds are increasingly recognized to have rapid effects on membrane surface receptors that often have not been identified at the molecular level. We show here that TRPM3, a divalent-permeable cation channel, is rapidly and reversibly activated by extracellular pregnenolone sulphate, a neuroactive steroid. We show that pregnenolone sulphate activates endogenous TRPM3 channels in insulin-producing beta cells. Application of pregnenolone sulphate led to a rapid calcium influx and enhanced insulin secretion from pancreatic islets. Our results establish that TRPM3 is an essential component of an ionotropic steroid receptor enabling unanticipated crosstalk between steroidal and insulin-signalling endocrine systems.

Strain uterography in labour

Multi-strain measurements of uterine contractions were made on 36 women at 36 to 42 weeks of pregnancy. The tracings obtained supported the existence of one dominant pacemaker area in the fundal region of the uterus and indicated that the contractile wave travelled in a downward direction with an average speed of 6 cm/second. The analysis of all normal labours showed that strains of the longitudinal muscle fibres changed from extension in the fundal region of the uterus to compression in its lower part, through a local zero strain in a narrow zone below the umbilicus. Intensity of the uterine contractions reached 6 per cent in extension and -2 per cent in compression. Information about the number of peak contractions, the frequenty of contractions and the tonus of the myometrium during relaxation are of importance in the evaluation of uterine dysfunction.