Thyroid hormones influencing renal electrolyte excretion in saline loaded rats of different ages.

Thyroid hormones are involved in the postnatal development of kidney functions. The influence of pretreatment with thyroid hormones on renal electrolyte excretion was measured in rats of different ages. Pretreatment with triiodothyronine or tetraiodothyronine (10 micrograms/100 g b.wt. i.p. for 3 days, once a day) cannot alter the low sodium excretion in young rats receiving a saline load. In 33-, 55- and 105-day-old rats the pretreatment with thyroid hormones is followed by a preferential increase of renal sodium excretion. Both thyroid hormones are effective.