Transcuticular solute movement in parasitic nematodes: relationship between non-polar solute transport and partition coefficient

The rate constants (K) for steroid transport across the isolated cuticle of Ascaris suum were, linearly related to partition coefficients (P) of steroids in model solvents. The slope of log P vs log K for an isolated cuticle was closest to unity for the more polar solvents, octanol and ether, suggesting that the barrier to steroid movement across the cuticle has partition properties similar to these solvents. The transcuticular movement of steroids into intact adult A. suum and infective larvae of Haemonchus contortus was predicted by the P in model solvents suggesting that the same barriers for transcuticular solute movement may exist in intact worms as in isolated cuticles.