Innervation of the renal cortical tubules: a quantitative study

A quantitative assessment of the innervation of the different portions of the cortical tubular nephron in the rat was made using tritiated norepinephrine uptake to label monoaminergic nerves, followed by autoradiography. The proximal tubules (PT) showed the greatest number of innervated profiles (IPs) [i.e., tubular profiles overlapped by accumulations of autoradiographic grains (AAG)] followed by the thick ascending limb of Henle (TALH), the distal convoluted tubule (DCT), and the collecting duct (CD). However, the highest relative frequency of innervation (RFI), i.e., the ratio of the number of IPs to the total number of profiles surveyed, occurred in the TALH followed by the DCT and PT. The number of IPs of the CDs was too low to permit adequate statistical evaluation. The PT showed the largest number of AAGs facing the interstitium or in contact with capillaries, while the TALH had the highest number in contact with the efferent arteriole. The DCT showed a disproportionately high number of AAGs in contact with the afferent arteriole. Our results suggest that all portions of the cortical tubular nephron are under some degree of neural influence.