Recently inter-individual differences of the expression of sodium- hydrogen-exchanger type 3 (NHE3) were found to inversely correlate with baseline ventilation in rabbits. Here, the expression of NHE3 mRNA in brainstem tissue of children died from sudden infant death (SID) and non-natural causes (controls) were compared. 26 male SID victims (4.6±3.2 months) were randomly selected from a larger collective and age-matched to 7 male controls (5.1±4.3 months). Careful autopsy protocols according to international guidelines were followed to distinguish between both groups. Yields of NHE3 mRNA, as quantified by real time RT-PCR, were not affected by post mortem intervals, storage time of tissue samples, and/or clotted blood adhering to the samples. Lowest and highest values within the SID group amounted to 0.03 and 1.06 fg cDNA/mg RNA, respectively. However, the mean value (±SEM) in the SID group was significantly higher than in the control group (0.26±0.05 vs. 0.14±0.02 fg cDNA/mg RNA, P<0.05). Other NHE-isoforms such as NHE1 and NHE5, whose mRNA contents were analysed in the same samples, showed no such differences.

Since NHE3 is involved in pH regulation of chemosensitive neurons and in the set point control of breathing, we suggest that a high NHE3 mRNA expression may increase the risk for SID.