Juxtaglomerular apparatus in the vertebrates

Abstract

Renin and juxtaglomerular (JG) cells are present in tetrapod vertebrates and teleosts the macula densa (MD) and extraglomerular mesangium (EGM) are seen only in mammals. Detailed studies of the evolution of juxtaglomerular apparatus (JGA) are presented in this paper. No granules were stained with Bowie's method in the kidneys of Chondrostei: Polypterus senegalus, Calamoichthys calabaricus, Acipenser brevirostris, and Holostein: Amia calva, Lepisosteus osseus. In the kidney of the lungfish, Protopterus aethiopicus, JG cells were found in the arterial wall distant from the glomeruli. Three types of distribution of JG cells were observed in aglomerular teleosts. In the kidney of Opsanus tau, JG cells were distributed in the walls of small arteries. In Lophius litulon, JG cells were distributed in several regions of the kidney. In Phrynelox nox, P. tridens and Histrio histrio, JG cells were concentrated in a limited area of the kidney. The MD site was examined with the light microscope in Gallus gallus v. domesticus and Coturnix coturnix japonica, and with the electron microscope in G. gallus. The avian cells possess some of the characteristics of mammalian MD cells, and can be considered as structurally transitional between typical MD cells in mammals and the ordinary cells of the distal tubule.