Osmolality of normal human saliva at body temperature.

IN AN ATTEMPT to establish normal osniotic pressure values for mixed humamm saliva, it was decided to measure the osnmolality of this biologic fluid by the vapor pressure lowering niethod reported earlier (1). It was found timat centrifugatioiu of the organic debris usually fommd in mixed saliva yielded a supernataimt fluid capable of benig analyzed by this technic. Samples of saliva were collected without stimulation from healtimy young adult male subjects 5 mm. after the subjects rinsed timeir mouths with tepid tap water. A )proXimately one-imalf of the samples were stored imi the frozen state for 1 year, and the other Imalf were analyzed for osmolahity within 1 week after collection. The specific instrument used imi this study was the Mechrolab vapor pressure osmometer Model 301. The principle 111)01) which time technic of time mstrumnent is based has been variously described. } ssentialiy, the metimod depends upon the vapor pressure lowerimug of a solvent by time presence of solute molecules or ions iii solution. A direct proportion is known to exist betweelm this value alid tlmat of the osmotic pressure. Among time advantages of the vapor pressure method of determining osmotic pressures over that of the freezing point lowering metlmod are the followiimg: (1) The temperature of measurement for biologic fluids can be set at body temperature instead of the freezing point of water. Ionization of solutes in biologic fluids is thus accounted for. (2) During operatiolm, the tenmperature of the apparatus is maintained at a constant level, to within ± 0.0010. Duplicate measurements of time osmotic pressure of fresh, unstimuhated, mixed saliva were made on 92 samples from normal young adult male subjects. The average osmolality for the series was found to be