Reaction of Rat Renal Medullary Laminin to Prolonged Dehydration

Laminins are the major water-soluble glycoproteins in the basement membrane of epithelial tissue. The laminin content of the renal parenchyma was studied in rats that were fed a 60-h alternative water diet with either excessive water intake or a complete lack of drinking water. It was shown that osmotic concentration of the urine, which develops due to water deprivation, is accompanied by a quantitative change in the laminin composition. It was found that the level of the laminin β chain increases in the renal medulla, but not in the renal cortex, of dehydrated rats. This effect occurs only in WAG rats with a normally expressed vasopressin gene and is absent in mutant Brattleboro rats unable to synthesize this hormone. Based on the initial and new data, it is assumed that laminin, as a key regulatory element in the basement membrane of the tubular epithelium, is involved in the adaptive response of the renal urine concentrating system to prolonged dehydration. Hyperhydration does not affect laminin levels in the renal parenchyma.