Differential distribution of the vasopressin V2 receptor along the rat nephron during renal ontogeny and maturation

Background. Ontogeny and cellular distribution of vasopressin receptors in the kidney are key factors determining the role of vasopressin in renal physiology. Expression of vasopressin V-2 receptor (V2R) mRNA and the immunoreactive protein in rat kidney were investigated. Methods. An antiserum directed to epitope TLD25 of the rat V2R sequence was characterized by Western blotting. Expression of V2R mRNA was assessed by reverse transcription-polymerase chain reaction (RT-PCR), and on protein level by immunohistochemistry. Results. Specificity of the antiserum was documented by Western blots from cells expressing a fusion protein of V2R and GFP. Using lysates of rat kidney and of native cell lines expressing-V2R but not V1R, our antiserum to peptide TLD25 revealed a major band of 55 kD corresponding to the monomeric form of V2R, and a band of 110 kD most likely representing the homodimeric form of the receptor. This highly specific antiserum allowed us to localize the V2R in thick ascending limbs, distal convoluted and connecting tubules, and in collecting ducts. During ontogeny, immunoreactivity was first observed at the luminal membrane on prenatal day 20, emerging at the basolateral side from postnatal day 5 on. RT-PCR demonstrated V2R transcripts from prenatal day 18 to gradually increasing thereafter. Conclusion. Expression of V2R is first detectable in the late embryonic stage of rat ontogeny starting from day E18 and gradually increasing with kidney maturation. In the adult kidney, V2R is differentially distributed in the various nephron segments.