Evidence for physiological regulation of myometrial gap junction permeability

We have investigated whether direct intercellular communication between uterine smooth muscle cells of delivering rats is influenced by intracellular adenosine 3',5'-cyclic monophosphate concentration ([cAMPi]) and agents relevant to the hormonal control of pregnancy and parturition. The rate of diffusion of phosphorylated 2-[3H]deoxy-D-glucose (2-DG) in strips of longitudinal myometrium from rats in labor, indicated by the apparent diffusion coefficient for this molecule, was observed to be significantly reduced in tissues with elevated [cAMPi] (after treatment with dibutyryl cAMP, 8-bromo cAMP, forskolin, and theophylline) in the absence of any change in the area of gap junctions (GJs). Similarly, several agonists that elevate [cAMPi] in this tissue (e.g., isoproterenol, relaxin, carbacyclin, prostaglandin E2) also reduced 2-DG diffusion. These data suggest that the permeability of GJs in uterine smooth muscle may be regulated by [cAMPi] and physiologically relevant agonists. Control of GJ permeability may be important for the physiological regulation of intercellular communication and the extent of synchronous contractile activity in the uterine wall during pregnancy and parturition.