Relaxing action of a holothurian toxin on mammalian smooth muscle

1. The crude epidermal mucous secretion produced by the sea cucumber Holothuria mexicana Ludwig inhibits the tonus and spontaneous mechanical activity of rabbit ileum at concentrations of 0.1 mg/ml and higher. 2. This effect, similar to that of epinephrine, is attributed to a compound referred to as mucotoxin (MuTX). 3. MuTX also relaxes strips of the rabbit aorta contracted by 10(-8) M norepinephrine and exerts a similar, less marked, effect on the same strips contracted in high potassium solutions. 4. These observations suggest that the relaxing effect of MuTX on mammalian smooth muscle is not mediated by an adrenergic mechanism.