Effect of hypertonic saline injections and water deprivation on drinking, serum osmolality and gut water

Abstract

Drinking was studied in rats water-deprived 0–60 hr and in satiated rats injected with 8 per cent NaCl by intraperitoneal, intravenous, subcutaneous, subcutaneous with procaine, and intragastric injections. The intraperitoneal injection produced the most drinking in 2 hr and the subcutaneous with procaine and the stomach injection produced the least. Water intakes increased with hr of deprivation. Serum osmolality and water content of the gut were measured in both water-deprived and salt-injected rats. The intraperitoneal and intravenous injections produced increases in serum osmolality as high as that produced by 60 hr of water deprivation, yet the deprived rats drank more than twice as much as the injected rats. The stomach injection produced almost no change in serum osmolality and the 2 subcutaneous injections caused a rise in serum osmolality slightly less than the intraperitoneal and intravenous injections. Both relative and absolute water content of the large and small intestine declined with hr of water deprivation. Salt injections affected relative water content of all the gut segments, but the nature of the change varied with the gut segment and the time after injection. None of the injections produced the loss in absolute gut water caused by 24–60 hr of water deprivation, although several injections produced relative gut water content equal to that produced by 60 hr of water deprivation. The intravenous injection produced a greater urine flow and a more rapid excretion of the salt load than any of the other injections.