REGULATION OF COLLECTING DUCT Na+ REABSORPTION BY ANP 31–67

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Abstract
SUMMARY: 1. The bulk of studies of the actions of atrial natriuretic peptides (ANP) have focussed on the carboxyterminal derivative (ANP 99–126) of the prohormone (ANP 1–126), but recent evidence indicates that an additional peptide derived from ANP 1–126, namely, ANP 31–67 also circulates, and has natriuretic actions.2. The effects of ANP 31–67 on inner medullary collecting duct (IMCD) Na+ transport have been examined in freshly prepared suspensions of rabbit IMCD cells. Like ANP 99–126, ANP 31–67 reduces Na+ transport in these cells.3. However, unlike ANP 99–126, this effect is not mediated by cGMP, and does not result from inhibition of apical Na+ channels. Rather, ANP 31–67 inhibits basolateral Na/K‐ATPase, probably via the stimulation of PGE2 synthesis.4. These results are discussed in the context of other natriuretic substances (interleukin 1 and endothelin), which also inhibit Na+ reabsorption by PGE2 ‐mediated inhibition of Na/K‐ATPase.