Loss of renomedullary interstitial cells in Brattleboro rats after vasopressin treatment.

Previous studies have shown a disappearance of interstitial cells from the renal medulla of rats with hereditary diabetes insipidus (Brattleboro) when the animals were treated with vasopressin in high doses. The present study was undertaken to elucidate the mechanisms behind this cell loss. The disappearance of interstitial cells from the renal medulla of Brattleboro rats was quantitatively determined by electron microscopic stereology after various types of treatment. A considerable decrease in the volume density of interstitial cells was induced by the administration of either 8-arginine vasopressin or 1-desamino-8-D-arginine vasopressin. This lesion of the interstitial cells was not prevented by the simultaneous administration of oxytocin. Even a 48-hour period of water deprivation also resulted in a slight decrease in the volume density of interstitial cells. The results indicate that the observed loss of renal medullary interstitial cells is not a direct effect of the hormone on the cells but probably secondary to the marked increase in the renal medullary solute (urea) concentration. The fact that animals with hardly any renomedullary interstitial cells concentrated their urine to a virtually normal level shows that these cells cannot play an important role in the concentrating mechanism. The interstitial cells recovered rapidly when the vasopressin treatment was discontinued, but it could not be determined whether this was due to local proliferation or to the immigration of cells from extrarenal tissue.