Plasma levels of arginine vasotocin, prolactin, aldosterone and corticosterone during prolonged dehydration in the domestic flowl: effect of dietary NaCl

Abstract

Three groups of White Plymouth Rock laying hens were adapted to three levels of dietary NaCl: low-NaCl food with tap water (LOW), high-NaCl food (1% NaCl w/w added) with tap water (HT), and high-NaCl food with 0.5% NaCl for drinking (HS). The birds were subjected to water deprivation (dehydration) for 18 days. Blood sampling was done at 2-4 day intervals. Plasma concentrations of arginine vasotocin (AVT), prolactin (PRL), aldosterone (ALDO) and corticosterone (CS) were determined by radioimmunoassay. Plasma osmolality, sodium, chloride, and potassium were also determined. In the normally hydrated hens fully adapted to the diets, there was a stepwise increase from LOW to HS in plasma osmolality (305, 315, 332 mOsm, for LOW, HT and HS, respectively), [Na+] (144, 153, 161 mM) and [Cl-] (109, 119, 127 mM) as well as in [AVT] (6, 14, 18 pg/ml) and [PRL] (16, 24, 34 ng/ml). Regressing [AVT] on osmolality gave a slope of 0.30 pg . ml-1/mOsm and a threshold of 273 mOsm. The slope of [PRL] on osmolality was 0.73 ng . ml-1/mOsm. The correlation coefficient of [AVT] and [PRL] was 0.67. LOW had high [ALDO] (165 pg/ml) which was suppressed to low levels in HT and HS (5-8 pg/ml), while [CS] was the same in all groups (0.9-1.1 ng/ml). Plasma [K+] was decreased in the high-NaCl groups (5.8 mM in LOW, 4.4 and 4.7 mM in HT and HS). Dehydration resulted within 2 days generally in a sharp (5-15%) increase in osmolality, [Na+] and [Cl-], which thereafter increased more slowly during the remaining 16 days in all groups, with the slowest increase in LOW. The levels of osmolality [Na+] and [Cl-] were 5% lower in LOW than in HT and HS, which showed the same levels during the dehydration period. Plasma [AVT] and [PRL] increased 2-4 fold within 2 days of dehydration; [AVT] reached a plateau at 29 pg/ml in all groups, but [PRL] continued to rise in all groups, fastest in LOW, reaching similar levels in all groups after 14-18 days of dehydration, about 85 ng/ml. The correlation coefficient of [AVT] and [PRL] was decreased by half (to 0.32) during dehydration. Plasma [ALDO] increased in all groups with dehydration, 1.7 fold in LOW and 3-6 fold in HT and HS, but the levels reached in HT and HS were only 15-30% of that seen in LOW.(ABSTRACT TRUNCATED AT 400 WORDS)

Localization of sodium absorption and chloride secretion in an intestinal epithelium

“…These responses are similar to those of Plymouth Rock hens (Clauss et al, 1988). Plasma aldosterone of the Cornish hens was 181 _+ 27 pg/ml (n = 21), very similar to values in Plymouth Rock hens (Arnason et al, 1986;Clauss et al, 1988) on the same dietary scheme.…”

“…They were fed a low-NaC1 diet, wheat and barley, and distilled water ad libitum for 14 days prior to experiments (Choshniak et al, 1977). After securing a blood sample for aldosterone analysis (Arnason et al, 1986), the birds were killed by neck dislocation. The lower intestine was quickly removed and the coprodeal epithelium dissected from its muscular layer and placed in 38~ oxygenated Ringer's (mmol/liter: 140 Na, 8 K, 1.3 Ca, 1 Mg, 139 CI, 1 SO 4, 8 PO4, and 15 glucose, pH 7.3).…”

House sparrows (Passer domesticus) increase protein catabolism in response to water restriction

“…The response of arginine vasotocin, prolactin, aldosterone, or corticosterone to water restriction could have provided insight into possible control of fuel selection during water restriction. However, this study did not differ substantially in terms of magnitude or duration of water restriction from many other studies that have thoroughly investigated the hormonal response to acute water restriction in birds at rest and during exercise (2,17,19,39). Corticosterone does affect fuel use in birds, and would be the likely hormone responsible for elevated lean mass catabolism.…”

Effects of adrenal steroids on Na transport in the lower intestine (Coprodeum) of the hen

“…As discussed previously (Thomas et al, 1980;Skadhauge et al, 1983;Arnason et al, 1986), the concentration of plasma aldosterone (PA) is high in low-NaC1 fed birds and decreased by resalination. The spironolactone dose in our study lowered PA level in one group of LS hens to about half the control values; in the second group with the higher spironolactone dosage, the PA level was below the limit of detection.…”

“…Recent investigators compared the different time-course of aldosterone injections (Thomas et al, 1980;Clauss et al, 1984) with the time-course of NaC1 depletion or restoration (Thomas & Skadhauge, 1979Skadhauge et al, 1983;Clauss et al, 1984). All these studies indicated a time-dependent dietary stimulation of Na transport, and that in spite of already augmented plasma aldosterone levels after two days (Arnason et al, 1986) 'it takes several days for the epithelium to achieve its maximal transport rate. Acute aldosterone injections do not stimulate Na transport to Current-voltage relations are determined before and after the addition of amiloride (as indicated by the arrows).…”