Modifications of the responses to antidiuretic hormone by hydrolytic enzymes

Abstract

Proteolytic enzymes (trypsin and α-chymotrypsin) and lipolytic enzymes (phospholipases A & C) have been used to treat both surfaces of the skins of frogs and toads. The effects of the enzymes on sodium transport (frog skin) and hydraulic flow (toad skin) have been measured, together with the effects on the responses to ADH. With the experimental conditions used, proteolytic enzymes reduced resting sodium transport but had no major effect on the responsiveness to ADH. Conversely these enzymes had no effect on resting hydraulic flow but reduced or abolished the responses to ADH. Phospholipases applied to the inner surfaces of skins affected neither water nor sodium movement but abolished the responses to ADH. Phospholipases applied to the outside enhanced the effect of ADH on water flow but had no effect on the increased sodium movement caused by ADH. The results are discussed in terms of the possible removal of calcium binding sites by phospholipases.