Stimulation of renal sodium excretion in mature rats

In adult rats a saline load is followed by an increase in renal excretion of sodium and by a low rate of ion exchange (hydrogen ions and potassium for sodium), caused by inhibited aldosterone secretion. Under analogous conditions a saline load provoked sodium retention and a distinct increase in renal excretion of hydrogen ions and potassium in young rats, which can be explained by a non-regulated, very intensive ion exchange. The repeated administration of NaCl solution alone and in combination with cyclopenthiazide produced an accelerated maturation of kidney function in 10- and 33-day-old rats measurable by an increase in sodium excretion and reduced ion exchange. In adult rats as well as immediately after birth (5-day-old rats) this effect cannot be provoked by the various pretreatments acting in mature rats.