We investigated whether physiological oscillations detected by non-contrast resting-state magnetic resonance imaging(rsMRI) can be used to measure functional nephron number, nephron density, or estimated single-nephron glomerular filtration rate(eSNGFR) in vivo. We further investigated whether the observed oscillations below 0.05 Hz reflect tubuloglomerular feedback(TGF). First, we compared features of spectral power of oscillations in rsMRI with total nephron number, nephron density, glomerular filtration rate(GFR), and eSNGFR in healthy Sprague-Dawley rats(N=20). We then compared features of spectral power to total nephron number in Zucker Diabetic Sprague-Dawley(ZDSD) rats(N=8) with type-2 diabetes. Finally, we tested the hypothesis that spectral features associated with nephron number reflect TGF by comparing spectra before and after furosemide infusion, which blocks the Na-K-2Cl co-transporter required for TGF and attenuates TGF oscillations. In healthy rats, the median power of rsMRI oscillations below 0.05 Hz in the kidney cortex was significantly correlated (p<0.05) with nephron number in all animals(R 2 =0.68) and within sex groups (R 2 ,males = 0.71; R 2 ,females = 0.73). Median power in this range was inversely correlated with eSNGFR(p<0.05, R 2 =0.39). No spectral features were correlated with nephron density or GFR. In ZDSD rats with confirmed pathology, total power between 0.015-0.045 Hz was significantly correlated with nephron number(R 2 =0.59, p<0.05). In both male and female rats, furosemide caused a significant attenuation of power in rsMRI spectral peaks below 0.05 Hz throughout the cortex(p<0.05). This work demonstrates the noninvasive, in vivo measurement of nephron number in healthy and diabetic rats using rsMRI, and the potential application of rsMRI to detect TGF-associated physiological fluctuations.
Baldelomar et al. (2026) studied this question.