Atrial natriuretic factor and vasopressin during dehydration and rehydration in rats

To determine the effect of water deprivation (mixed volume and osmotic stimulus) on the secretion of atrial natriuretic factor (ANF) and arginine vasopressin (AVP), plasma immunoreactive ANF (IR-ANF), and plasma AVP were measured in normal conscious Sprague-Dawley rats. IR-ANF was decreased to 19.9 +/- 3.6 pg/ml (24 h dehydration), 9.8 +/- 2.5 pg/ml (48 h dehydration), and undetectable level (72 h dehydration) from the control level of 62.4 +/- 2.4 pg/ml. These decreases were accompanied by significant increase in plasma AVP, serum Na+, osmolality (osm), and hematocrit (Hct). In animals deprived of water for 3 days the secretion of ANF and AVP was monitored at seven time points during the 1st h after voluntary rehydration with tap water. After rehydration, IR-ANF was elevated dramatically within 3 min and gradually for up to 1 h after water was offered; AVP decreased within 3 min of rehydration and stayed at the water-repleted level during the next 1 h. Na+, osm, and Hct did not change until 15, 9, and 30 min after rehydration, respectively. The rapid modifications in plasma IR-ANF and AVP were accompanied by a transient but significant increase in arterial blood pressure for up to 15 min after water consumption. These results indicate that oropharyngeal-gastric stimuli contribute to the release of both ANF and AVP.