Atrial natriuretic peptides (ANP) are potent effectors of volume homeostasis in mammals, but their effects on fluid compartments in teleost fish are unknown. In the present study, whole-body blood volume (BV: 51Cr-red cells), and extracellular fluid volume (ECFV; 58Co-EDTA space), and 51Cr-red cell and 58Co-EDTA space in 31 tissues was measured in unanesthetized trout infused for 8 h with saline (1.2 ml·h-1·kg-1) or with rat atrial natriuretic peptide (Ile-26; ANP) at a rate of (300 ng·h-1·kg-1 at 1.2 ml·h-1·kg-1). Urine flow was also measure and 58Co-EDTA clearance provided an index of glomerular filtration (GFR). ANP infusion significantly decreased BV from 29.0±1.2 (n=22; saline) to 22.9±1.0 ml·kg-1 (P≤0.01, n=22; ANP) and ECFV from 242±17 (n=14; saline) to 170±6 ml·kg-1 (P≤0.001, n=14; ANP); therefore, the majority of the fluid lost is from the interstitial compartment. ANP increased red cell space in gill, pectoral fin, brain, eye, and bulbus, presumably through local vascular effects, and decreased it in caecum. ANP decreased ECFV in anterior kidney, liver, gill, anterior intestine, posterior intestine, caecum, swimbladder, gall bladder, operculum, skull, pelvic fin and dorsal skeletal muscle. ECFV was also slightly reduced by ANP infusion in all other tissues, although not significantly, suggesting a general extracellular dehydration. Urine excretion and GFR increased (P≤0.01) from 2.9±0.4 and 5.7±0.1 ml·h-1·kg-1 in saline infused trout (n=11, 9, respectively) to 6.3±0.8 and 12.7±2.3 ml·h-1·k-1 in ANP infused trout (n=15, 12, respectively). These data show that ANP is hypovolemic in trout and that an increased GFR is the principal mechanism through which urine output is increased. Increased urine formation, however, can only account for 40% of the decrease in extracellular fluid volume. Translocation of extracellular fluid into other compartments, including intracellular compartments must be considered.
|Original language||English (US)|
|Number of pages||6|
|Journal||Journal of Experimental Zoology|
|State||Published - Jul 1 1997|
ASJC Scopus subject areas
- Animal Science and Zoology