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Camels thrive in arid and semiarid areas, although food and water frequently are scarce. However, the mechanisms enabling camels to withstand food deprivation are poorly understood. In this study four female camels were totally deprived of food for 4 days. Their body weight decreased by 6%. Food deprivation caused no change in total plasma protein concentration in the camel, indicating that no alterations in plasma volume occurred. When the first meal was withheld water intake was unchanged. Next day the camels showed signs of hydration with a decreased plasma Na+ concentration and an increased excretion of diluted urine. In the afternoon water intake decreased. Urine K+ excretion fell the first day and urine volume and Na+ excretion from the third day. No activation of the renin-angiotensin-aldosterone system (RAAS) was observed. Plasma and urine urea concentration increased during food deprivation. Plasma glucose concentration and plasma cortisol and thyroxine levels did not change. Body temperature decreased during food deprivation. After refeeding, total plasma proteins increased temporarily by 12%, and a threefold increase in RAAS was seen, implying that both plasma volume and RAAs changed rapidly. Our results show that fluid balance was only slightly affected in the food-deprived camel. We suggest that strategies for the camel to endure food deprivation include maintenance of plasma volume and glucose concentration and a lowering of the body temperature.

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This study was designed to examine the actions of ANP in acute, ANGII-mediated hypertension during pregnancy. Effects on blood pressure, blood volume, and renal Na and K excretion were evaluated in conscious goats (n = 6). ANP (2 micrograms min-1), ANGII (0.5 microgram min-1), or ANGII+ANP (doses the same as for each peptide alone) was infused intravenously for 60 min. The pressor response to ANGII was reduced in pregnant goats. This reduction was seen in systolic, but not in diastolic pressure. ANP decreased pressure by 5-10 mmHg both in pregnancy and in non-pregnancy. When ANGII+ANP was infused, blood pressure initially rose as with ANGII but then declined. ANP suppressed only the elevated systolic pressure. Plasma protein concentration and haematocrit was reduced by ANGII but increased by ANP alone or together with ANGII, thereby implying fluid shift into the vasculature by ANGII and opposite movement by ANP. ANGII increased renal Na excretion to 1500 mumol min-1 in non-pregnancy, but only to half of that in pregnancy. ANP alone caused small natriuresis, but enhanced ANGII-induced natriuresis to near 3000 mumol min-1 in both non-pregnant and pregnant goats. In summary, ANP further attenuated the blunted blood-pressure rise due to ANGII in pregnant goats, and reduced plasma volume, but enhanced renal Na excretion as in non-pregnant goats. This implies that with the present combination ANP and ANGII caused a near maximal natriuretic response that was not modified by the systemic cardiovascular changes occurring in pregnant goats.