Effects of Acetylcholine on the Clearance of [3H]-Antipyrine in Bilaterally Perfused Lobules of Human Term Placenta

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Abstract
Single located lobules from human term placenta were bilaterally perfused with a balanced salt solution. The clearance of [3H]-antipyrine from the maternal to the fetal circulation was measured in an open perfusion circuit (no recycling). Acetylcholine (ACh, 10 and 100 .mu.M) was added to the meternal perfusate to examine the hypothesis that ACh may control permeability and transport processes across the placental membranes. ACh reduced the flow- and diffusion-limited clearance of [3H]-antipyrine in a reversible manner. Similar effects were obtained with physostigmine (eserine, 10 and 100 .mu.M), an inhibitor of choline ester hydrolyzing enzymes, and ACh acted synergistically on this clearance reduction.