NMDA NR3A and B subtypes are differentially expressed in the developing rat kidney

The N‐methyl‐d‐aspartate (NMDA) receptor is a widely recognized glutamate receptor in the brain. The NR3 subtype is only found in developing brain. Its exact function in the kidney is unknown. Interestingly, the NR1/NR3 receptor complex requires only glycine rather than a combination of glycine and glutamate to activate the channel. Male and female rat kidneys were examined at post‐partum day 1, 7, 14 and 21 for NMDA content. Protein was analyzed via Western blot and histological sections were examined via fluorescent confocal microscopy. Semi‐Quantitative PCR confirmed the presence of NR3A and B. Our studies show the presence of the NMDA NR3 receptor subtypes in the rat kidney. Interestingly, the NR3A is only found in the collecting ducts, whereas NR3B is widely expressed in all tubules EXCEPT the collecting duct. In addition, the NR3 subtype is expressed early in kidney development and protein expression peaks at 7–14 days after birth and then disappears. There are also gender‐dependent differences in NR3B expression, with females having lower levels and peaking at day 7, whereas males have higher levels of NR3B expression and peak expression later, at day 14. RT‐PCR results parallel the protein expressions. These results echo our previous results of higher NR2A expression in males and also point to possible developmental differences in the NR3 expression.