Hi Brandi,
I think the pits do have a toxin in them (small amounts), but the leaves are the real issue, from what I've read. Okay, did a lookup, see below: all parts, especially when wilted. From the note below, not sure if it includes cultivated varieties, but I'd rather be safe than sorry...
Lori
Here's an excerpt from
OSU's Extension bulletin:
WILD BLACK CHERRY, CHOKE CHERRY, AND PEACH (Prunus spp.) – Many species of cherry and peach are poisonous. These species are characterized by alternate toothed leaves, white or pink flowers, and fleshy fruits (cherries or peaches). Crushed twigs and leaves yield a strong cyanide odor. Two native species of cherry are common in Ohio. Wild black cherry (P. serotina) is a large tree that is distributed widely throughout the state in woodlands, old fields, and along fence rows. Choke cherry (P. virginiana) grows as a large shrub or small tree and is scattered throughout Ohio in a variety of habitats, though it is more frequent northward. Peach (P. persica) is a small introduced tree that occasionally escapes from orchard cultivation through seed.
Seeds, twigs, bark, and leaves contain a glycoside (amygdalin) that quickly breaks down by hydrolysis (from bruising, wilting, frost damage) to form the highly toxic compound hydrocyanic (prussic) acid (or cyanide). Poisonings occur most frequently when wilted leaves are eaten, but have also been reported when leaves are consumed directly from the tree, or sprouts, or in dried hay. The amount of hydrocyanic acid formed once the plant material is ingested is affected by the type of stomach juices and the kind of feed the animal had previously consumed. Ruminant animals appear to be more susceptible to poisoning than horses.
Cyanide poisoning results in hypoxia (deficiency of oxygen reaching the tissues). The first symptoms appear within a few minutes following consumption of plant material. Affected animals exhibit excitement, incoordination, convulsions, rapid and labored breathing, bloating, and coma. Death can occur in less than an hour due to internal asphyxiation.