Maryanne R. Hughes

The effects of hypertonic sodium chloride injection on body water distribution in ducks (an as platyrhynchos), gulls (Larus Glaucescens) and roosters (Gallus Domesticus)

Abstract 1. Plasma volume was measured by T-1824 dye dilution and extracellular (ECF) fluid and total body water (TBW) by 82 Br and 3 H 2 O dilution in fresh (FW) and salt water (SW) acclimated Peking ducks, Anas platyrhynchos , and fresh water acclimated gulls, Larus glaucescens , and White Leghorn roosters, Gallus domesticus , before and after intravenous injection of hypertonic NaCl. 2. Plasma volume (%BW) was least in the rooster, 4·4%, and greatest in the gull, 7·2%, but these relationships did not hold when data was expressed as % TBW. When referred to TBW, the rooster remained lowest, 7·8%, but the ducks were highest, FW, 9·2% and SW, 10·6% and the gulls were 8·1%. 3. ECF, calculated as % BW, was essentially the same in FW ducks, 24·9%; SW ducks, 26·4% and roosters, 28·8%, but higher in gulls, 38·2%. When calculated as % TBW FW ducks were 36·4%; SW ducks were 41·3% and gull, 43·6% while the rooster was 52·9%. 4. TBW calculated as % BW was least in the rooster, 54·3%; greatest in the gull, 87·9% and intermediate in the ducks, FW duck, 68·5% and SW duck 64·0% respectively. 5. Injection of 0·2% body weight 5·0 N NaCl caused increases of more than 20% in the extracellular sodium concentration in all birds, however, secretion from the salt glands was observed only in birds which also had a significant increase in ECF volume implicating volume receptors in the stimulatory sequence leading to salt gland secretion.

Total Body Water and Its Turnover in Free-Living Nestling Glaucous-Winged Gulls with a Comparison of Body Water and Water Flux in Avian Species with and without Salt Glands

Total body water (TBW) and its turnover were measured in free-living nestling glaucous-winged gulls Larus glaucescens. Body mass (BM) was linearly related to age, and TBW was linearly related to BM in nestlings aged 4-38 days. Equilibration of intravenously (i.v.) injected tritiated water (TOH) was complete in ½ h; intraperitoneally (i.p.) injected TOH in 1 hour. TBW, ml = -28.4 + 0.88 BM, g(r² = .99; 48 determinations, TOH dilution in nestling gulls). TBW decreased rapidly at the end of the maturation period with the largest nestlings (5) having TBW of 83.2% BM, which was higher (P < .001) than that of fledglings (5), 73.9% BM, which was higher (P < .025) than that of adults (5), 66.0% BM. TBW by TOH dilution exceeded that by desiccation to constant weight. Tissue tritium retention in growing gulls was negligible. Mean daily water flux (WF) in adult gulls (6) was 18.1% BM, and mean daily nestling water efflux (WE) was 28.6% BM, linearly related to BM over the growth period and the same during rainy and fair periods. Analysis of published data TOH studies showed that species with salt glands tended to have higher TBW and had significantly (P < .05) greater water flux: WF = 1.03 BM0.75 than species lacking salt glands, WF = 0.52 BM0.73.

Comparison of renal and salt gland function in three species of wild ducks.

SUMMARY Three processes central to osmoregulation of marine birds were compared in three species of ducks that differ in habitat affinity, diet and saline tolerance. These processes are filtration of Na+ and water from the plasma by the kidneys, their reabsorption along the renal tubules, and secretion by the salt glands. Barrows goldeneyes Bucephala islandica, the most marine species, have the highest rates for all three processes and only this species can secrete all the infused salt via the salt glands. Rates of all three processes are lower in mallards Anas platyrhynchos, the most freshwater species. Following saline acclimation, mallards could excrete all the infused Na+ by a combined Na+ excretion of the kidneys and salt glands. Canvasbacks Aythya valisineria, despite being more saline tolerant than mallards, are unable to excrete all the infused Na+. They produce a large volume of urine (like mallards) that has a low [Na+] (like goldeneyes). Salt gland secretion Na+ concentration did not differ among the three species, but only goldeneyes secrete at a rate sufficient to eliminate all infused Na+ via the salt glands. Differences in saline tolerance of these ducks species cannot be fully explained by differences in their filtration, reabsorption and secretion of Na+ and water, suggesting that the intestinal tract plays an important role.

Cloacal and salt-gland ion excretion in the seagull, Larus glaucescens, acclimated to increasing concentrations of sea water

Abstract 1. 1. Gaucous-winged gulss, Laurs glaucescens, were acclimated sequentially to fresh water, 1 3 , 2 3 and 3 3 sea water for periods of 1–2 months. Sodium, K and Cl concentrations in the plasma (no K values), cloacal fluid and NaCl-induced salt-gland secretion were determined (spontaneous salt-gland secretion was analyzed when observed), and body weight and hematocrit were recorded weekly. 2. 2. Plasma Na concentration was lower in fresh-water birds than in birds acclimated to 1 3 sea water. Increased salinity of the drinking water had no further effect. Chloride concentration was the same in birds on all drinking water regimes. 3. 3. In only 12 of 331 cloanal fluid samples was Na hypertonic to plasma; in only 35 of 336 samples was Cl hypertonic. 4. 4. Cloanal retention of fluid lowered its Na and Cl but increased (or did not change) K concentration. 5. 5. In NaCl-induced salt-gland secretion Na and Cl concentration were higher in 1 3 sea water than in fresh-water-acclimated gulls, but further increase in drinking water concentration did not enhance this effect; K concentration of sea-water-adapted birds was twice that of fresh-water birds. The Na : K ratio in fresh-water birds was 24 : 1, 12 : 1 in sea-water birds. 6. 6. Hypertonic spontaneous salt-gland secretion was observed in gulls drinking fresh water to 2 3 sea water. Ion concentration increased as drinking-water concentration increased, but Na and Cl were not always of similar concentration as in NaCl-induced secretion. 7. 7. Body weight and hematocrit were lower in gulls adapted to sea water than in fresh-water birds. 8. 8. These data further suggest that a major portion of ingested. Na and K may be extrarenally excreted even in the absence of imposed osmotic stress and that the cation concentration in the salt-gland secretion is dependent upon the magnitude of the osmotic stress.

EFFECT OF CADMIUM ON PEKIN DUCK TOTAL BODY WATER, WATER FLUX, RENAL FILTRATION, AND SALT GLAND FUNCTION

The following hypotheses were examined using Pekin ducks (Anas platyrhynchos) as a model for marine ducks: cadmium (Cd) intake affects (1) salt gland and/or kidney function of ducks and (2) osmoregulation differently in male and female ducks. Birds were fed 0, 50, or 300 microg Cd/g food. They were gradually acclimated to 450 mM NaCl and then drank 300 mM NaCl for 3 mo while salt gland secretion (SGS), glomerular filtration rate (GFR), total body water (TBW), and water flux (WF) were measured in ducks eating control and high-Cd diets. Cadmium ingestion did not markedly affect body mass, but significantly enlarged the salt glands and kidneys. Enhancement of kidney mass was greater in males. Cadmium ingestion did not affect TBW or WF, but tended to increase interstitial fluid space at the expense of intracellular fluid. Sex did not affect TBW, but males had greater WF. Birds that ate Cd diets, especially the higher Cd diet, exhibited renal tubular damage and lower GFR. Ducks that ate Cd had lower plasma sodium concentration and osmolality and, to activate SGS, required longer infusion of NaCl and larger incrementsThe following hypotheses were examined using Pekin ducks (Anas platyrhynchos) as a model for marine ducks: cadmium (Cd) intake affects (1) salt gland and/or kidney function of ducks and (2) osmoregulation differently in male and female ducks. Birds were fed 0, 50, or 300 mug Cd/g food. They were gradually acclimated to 450 m M NaCl and then drank 300 m M NaCl for 3 mo while salt gland secretion (SGS), glomerular filtration rate (GFR), total body water (TBW), and water flux (WF) were measured in ducks eating control and high-Cd diets. Cadmium ingestion did not markedly affect body mass, but significantly enlarged the salt glands and kidneys. Enhancement of kidney mass was greater in males. Cadmium ingestion did not affect TBW or WF, but tended to increase interstitial fluid space at the expense of intracellular fluid. Sex did not affect TBW, but males had greater WF. Birds that ate Cd diets, especially the higher Cd diet, exhibited renal tubular damage and lower GFR. Ducks that ate Cd had lower plasma sodium concentration and osmolality and, to activate SGS, required longer infusion of NaCl and larger increments in extracellular osmolality and volume. Cadmium ingestion did not affect SGS rate or [Na+]. Both hypotheses were accepted since birds that ate Cd had lower GFR and delayed onset of SGS in response to salt challenge and the effects of Cd on the size and response of excretory organs were sexually disparate. Cadmium appeared to compromise the salt excretion of Pekin ducks. However, they are less salt tolerant than seaducks and, in this study, had higher organ Cd concentrations than those seen in wild ducks. Further studies are needed to determine if these observations also apply to the more salt-tolerant seaducks.

Effects of caecal ligation and saline acclimation on plasma concentration and organ mass in male and female Pekin ducks, Anas platyrhynchos

SummaryThe intestinal caeca reabsorb urinary sodium chloride (NaCl) and water (Rice and Skadhauge 1982). Free water may be generated if the reabsorbed NaCl is secreted via salt gland secretion (Schmidt-Nielsen et al. 1958). Therefore ceacal ligation should (a) reduce hingut NaCl and water reabsorption, (b) enhance the increase in plasma osmolality during saline acclimation, and (c) affect drakes more than ducks. Twelve Pekin drakes and 13 Pekin ducks, Anas platyrhynchos, were caecally ligated or sham operated before acclimation to 450 mmol · 1 NaCl. Body mass, hematocrit, plasma osmolality, and inonic concentrations of plasma, cloacal fluid, and salt gland secretion were measured after each increase in drinking water salinity. Osmoregulatory organ masses were determined. Caecal ligation did not effect plasma osmolality or ion concentrations of plasma, cloacal fluid, or salt gland secretion, but reduced salt gland size in ducks. Drakes and ducks drinking fresh water had the same hematocrit, plasma osmolality, and plasma concentrations of Na+ and Cl−. In both sexes exposure to 75 mmol · 1-1 NaCl significantly decreased plasma [Na+] and doubled cloacal fluid [Na+]. Exposure to 450 mmol · 1-1 NaCl decreased body mass and increased hematocrit, plasma [Na+], [Cl−], and plasma osmolality (more in drakes than in ducks); cloacal fluid osmolality nearly doubled compared to freshwater-adapted ducks, due mainly to osmolytes other than Na+ and Cl−. The [Cl−] in salt gland secretion only slightly exceeded drinking water [Cl−].

Total body water volume and turnover rate in fresh water and sea water adapted glaucous-winged gulls, Larus glaucescens

Abstract 1. 1. Total body water (TBW) volume and TBW turnover rate were measured by tritiated water (THO) disappearance rate in glaucous-winged gulls, Larus giaucescens drinking either fresh water or sea water. These measurements were compared allometrically to values reported for other birds. 2. 2. TBW volume was 79 ± 3% B W and TBW turnover 0.064 ± 0.006 ml/g day in birds given fresh water. These values did not change when these birds were later adapted to sea water. 3. 3. TBW volume is large in gulls compared to other species. TBW turnover rate of gulls is similar to that of other species.

Glomerular filtration rate in saline acclimated ducks, gulls and geese

1. 1. Glomerular filtration rate was estimated by measurement of cloacal excretion of intramuscularly injected 14C PEG in fresh water and sea water acclimated Mallards, Anas platyrhynchos, Canada Geese, Branta canadensis, and Glaucous-winged Gulls, Larus glaucescens. 2. 2. GFR (ml/min kg) of FW Mallards was 3.3 ± 1.8 (5); FW geese, 1.2 ± 0.1 (2) and FW gulls, 1.9 ± 0.4(4). 3. 3. Acclimation to SW did not affect the GFR of ducks, but increased the GFR of geese, 2.2 ± 0.1 (2) (P < 0.0005) and gulls, 4,0 ± 0.3 (5) (P < 0.005).

Flow rate and cation concentration in salt gland secretion of the glaucous-winged gull, Larus glaucescens

Abstract 1. 1. The sodium and potassium concentrations of 118 NaCl-induced salt gland secretion samples of the gull, Larus glaucescens, were analyzed as functions of secretory flow rate. 2. 2. Sodium concentration was positively correlated with flow rate; potassium concentration was negatively correlated. These relationships were not noted in birds drinking fresh water. 3. 3. The slope of the sodium regression line was little affected by drinking-water salinity, while that of potassium was greatly steepened.

Hypertonic salt gland secretion in the glaucous-winged gull, Larus glaucescens, in response to stomach loading with dilute sodium chloride

1. 1. Hypertonie salt gland secretion (SGS) Na, 375; K,27; Cl, 463m-equivl. was noted within 45 min of observation in four of eight nonloaded glaucous-winged gulls, Larus glaucescens. The time was the same for gulls stomach loaded with 150 m-equivl. NaCl; increased to 77 min in 100 and decreased to 9 min in 300 m-equivl. NaCl loaded birds. 2. 2. Loading with hypotonie NaCl (5 per cent body wt. 100 m-equivl. NaCl) increased SGS Na to 525 and K to 51 m-equivl. (P <0·05). 3. 3. Birds loaded with isotonic NaCl (150 m-equivl.) had twice the total extrarenal Na secretion (1·5 m-equiv. daily) of nonloaded birds (P <0·001). 4. 4. Hypertonic secretion was noted in nonloaded, 100 and 150 m-equivl. NaCl loaded gulls from which the supraorbital glands had been removed.