Control of body fluids and saline intake in hamsters

Abstract

Nondeprived hamsters resist increases of saline intake, even though the consequences may include weight loss or death (e.g., after adrenalectomy), but fluid-deprived hamsters will increase isotonic saline intake more than water consumption during rehydration. Experiment 1 examined plasma volume and body water changes during rehydration to see if residual saline drinking could be accounted for by a differential repletion of the extracellular space. Results showed that water and saline were equally effective in replacing lost plasma volume, but that saline intake produced up to 25% plasma expansion. Together with a previous finding of increased positive 24-hr sodium balances during saline rehydration, the observed plasma expansion suggests an explanation for increased saline intake based on a delay of cellular rehydration secondary to sodium retention rather than a mechanism of sodium appetite or “hypovolemic” drinking. Other desert-adapted species reportedly show a similar saline aversion and sodium retention. Experiment 2 asked whether hamsters would increase saline intake after fasting in order to maintain a normal rate of refeeding. Saline intake did not increase, and refeeding, like ad lib feeding, was depressed by saline consumption. Thus, hamsters increase saline intake in defense of fluid, but not energy, balance.