[Possible role of ammonium as a paracrine regulator in the uterine tissue]

An opportunity of formation of ammonia (NH3) in utera endometrium and its influence on exchange of Ca2+ and H+ in plasmalemma of myometrium was investigated. Dissociation of endometrium stroma cells and myocytes suspension was carried from utera of pigs and rats in accordance with the traditional techniques. In suspension of stroma cells a rather high AMP-deaminase activity (53 +/- 2 mmol IMP/hour on 1 mg of protein) was determined. It was demonstrated that ammonia release in extracellular space (measured by the changes of colouring of trinitrobenzolsulfonate acid) was significantly amplified by 1 mM acetylcholine and decreased by 0,1 mM fluoride ions, nonspecific AMP-deaminase inhibitor. It enables to assume a role of AMP-deaminase in formation of NH3 by endometrium stroma cells and its release into extracellular space during acetylcholine stimulation. The addition of ammonia (4 mM) to suspension of myocytes is accompanied by significant increase in pH (measured by the change in BCECF fluorescence) in extracellular and intracellular space, and the last parameter is inhibited by the blockers of passive H+ transport across the membrane: 0,1 mM 4-aminopyridine and tetraethylammonium. It is possible that addition of ammonia-containing solution results in increase in proton gradient on myocyte membrane and in amplification of H+ efflux. The opportunity of stimulation ofacetylcholine-activated passive Ca2+ transport in myocytes by 4 mM NH4+ that was suppressed by 1 mM cadmium and 1 nM nifedipine was also shown using fluorescent probe FURA-2AM. The increase in Ca2+ concentration in cytoplasm in the given conditions is intensively oppressed by protonophore (0.04% 2,4-dinitrophenol) and is effectively amplified by Na+/H+-exchange inhibitor 0,1 mM amyloride. It is possible to assume an amplification of lygand-activated passive Ca2+ transport caused by dispersion of transmembrane proton gradient which exists on plasmalemma and can be increased by ammonia formation in endometrium. The role of diffused from endometrium NH3 in regulation of utera functional activity requires further investigation, however already at this stage it is possible to assume, that NH3 molecules (or ion NH4+) can carry out a role of paracrine regulator in the system endometrium-myometrium.