CHARACTERIZATION AND DISTRIBUTION OF CHOLINESTERASE ACTIVITY IN MOUSEUTERINE HORNS - CHANGES IN ESTROUS-CYCLE

1. Both butyrylcholinesterase (BChE) and acetylcholinesterase (AChE) a re present in the mouse uterus, BChE being more abundant. 2. Their mol ecular forms were sequentially solubilized by different extraction med ia obtaining three ChE fractions whose specific activity was different , depending on the stage of the estrous cycle: hydrosoluble (estrous: 75.5 +/- 6.6 and diestrous: 47.9 +/- 8.7 mU/mg prot); detergent-solubl e or amphiphilic (estrous 26.6 +/- 2.4 and diestrous 14.7 +/- 3.3 mU/m g prot.), and high ionic strength-soluble (estrous: 18.7 +/- 4.2 and d iestrous 12.8 +/- 1.2 mU/mg prot.). 3. Histochemical procedures demons trated a different distribution for both ChE activities. AChE was foun d in nerves next to smooth muscle cells of the circular layer and bloo d vessels, while BChE was concentrated in the longitudinal stratum sur rounding the smooth muscle cells. Under the predominance of progestero ne, BChE was also found in the endometrial glands. 4. Maximal contract ions evoked by the addition of ACh to the isolated organ bath were con centration dependent and greater in estrous than in diestrous. Neverth eless the difference at the two stages of the estrous cycle disappeare d when contractions were normalized to smooth muscle cross-sectional a rea. 5. BChE but not AChE inhibition augmented maximal contractions el icited by ACh in longitudinal but not in circular smooth muscle. 6. Th e effect of BChE inhibition on the contractile force developed was gre ater at lower concentrations of ACh and did not depend on the stage of the estrous cycle.