THE EFFECTS OF A HIGH SODIUM DIET ON THE METABOLISM AND SECRETION OF VASOACTIVE-INTESTINAL-PEPTIDE IN THE RABBIT

1. In view of previous observations that; the metabolism of vasoactive intestinal peptide (VIP) is significantly increased in sodium-depleted rabbits, we wished to determine whether a high sodium intake also leads to alterations in VIP metabolism. We performed metabolic clearance studies in rabbits maintained on a high sodium diet and normal control diets. These studies were performed both before and after the administration of 1.5 mmol kg-1 of sodium intravenously to observe the effects of an acute increase in body sodium. 2. The rabbits maintained on the high sodium diet had a significantly lower basal plasma VIP level (P < 0.025). a lower metabolic clearance rate (MCR) of the peptide (P < 0.025) and a lower secretion rate (P < 0.005), compared with the normal control animals. These differences were maintained following the intravenous sodium infusion. 3. The administration of the intravenous sodium infusion resulted in a further decrease in MCR in the rabbits on the high sodium diet (P < 0.05). 4. These results confirm that VIP metabolism is affected by high dietary intake of sodium, as well as a low sodium intake, adding further support to the hypothesis that VIP may be involved in sodium homeostasis.