Acute Experiments on the Volume of the Urine
Allowed free access to water, dogs drink enough to prevent dehydration, but not more than this (Chapter 21). Consequently the dog in the basal state, at rest, 16 hours after a meal and having had recent access to water, is neither over- nor under-hydrat-ed. In the few available observations, plasma concentration of vasopressin in this state averaged 3.5 pmol/litre (1.5 m-u/litre), corresponding as described on p. 190 to the release of ADH at about 0.2 m-u/min. From this state, increased release of ADH cannot have any large effect on the urine, since the action on the kidneys is already nearly maximal (Fig. 34, p. 171). Tables 3, 8, 13, 14, 15 (p. 8, 58, 80, 89, 99) showing the increased excretion of urinary solutes record the composition of the urine always in the presence of adequate ADH and changes in the release of ADH are not involved; the urine is always concentrated and the volume remains small. Later in this chapter, in describing water diuresis in normal dogs, the urine in the absence of ADH becomes of low concentration and high volume.
KeywordsUrine Volume Urine Flow Distal Tubule Stomach Tube Osmotic Diuresis
Unable to display preview. Download preview PDF.