Expression of aquaporin-1 (AQP1) in the adult and developing sheep kidney.

The distributions of aquaporin-1 mRNA and protein were studied by hybridization histochemistry with a homologous riboprobe and immunohistochemistry, in the adult sheep kidney. Heaviest labelling occurred in the thin descending limb (DTL) of the loop of Henle in the inner stripe of the outer medulla, with apparent decreasing expression in the inner medulla, outer stripe of the outer medulla and cortex, but no quantitation was performed. Only proximal tubules (PT) (convoluted and straight) and DTL labelled. The glomerulus showed no labelling, consistent with the pattern in the rat but different to that in the human. During ontogeny, no labelling occurred in the mesonephros at 27 or 41 days of gestation (term = 145-150 days) but other structures did label at 27 days (heart, lung bud, blood vessels surrounding developing spinal cord). Labelling first occurred faintly in the metanephros at 41 days of gestation and increased throughout gestation consistent with morphological development of nephrons.