Okajimas Folia Anat. Jpn., 63(6): 393-406, March 1987 Fine Structural Changes in the Three-Dimensional Structure of the Rat Juxtaglomerular Apparatus in Response to Water Deprivation By Sumie KIDOKORO Department of Anatomy, Yokohama City University School of Medicine, Kanazawaku, Yokohama, 236 Japan -Received for Publication, December 26, 1986- Key Words: juxtaglomerular apparatus, reconstruction, ultrastructure, water deprivation, rat Summary: Morphological changes in the juxtaglomerular apparatus (JGA) after water de- privation, especially those in the spatial relationships among the structural components of the JGA were investigated by electron microscopy of serial sections and the three-dimen- sional reconstruction. The most remarkable changes were observed after 1-day-water depriva- tion, i.e. the secretory granule-containing cell layer in the afferent arterioles was markedly increased in extent, and the ratio of contact area between the Goormaghtigh cells (GoCs) and the macula densa of the distal tubule to the whole surface of the GoC field was signifi- cantly reduced. A possible role of the GoCs in function of the JGA was discussed. The morphology of the juxtaglomerular a functional system for tubulo-glomerular apparatus (JGA) has been intensively studied feedback mechanism. It has been described by various approaches, including three- that the JGCs are also found in the efferent dimensional study using reconstruction arteriole as well as in the extraglomerular of serial sections (Barajas & Latta, '63; mesangial cells in some occasions. It is Faarup, '65; Barajas, '70; Christensen et al., generally recognized that several factors are '75; Christensen & Boll , '78; Gorgas, '78; involved in the control mechanism for Christensen et al., '79; Spanidis, '82), freeze- renin release: Changes in blood pressure, fracture replicas (Pricam et al., '74; Boll et sodium balance in body fluid as well as in al., '75; Forssmann & Taugner, '77; Taugner blood plasma, nerve stimulation, Immoral et al., '78), immunocytochemistry (Edelman agents including adrenaline, noradrenaline, & Hartroft, '61; Sutherland, '70; Taugner angiotensin II, antidiuretic hormone and et al., '79; Phat et al., '81; Taugner et al., others [see reviews of Keeton & Cambell '81; Fraggiana et al ., '82) as well as conven- ('84), Wright ('84), and Briggs '('85)]. A tional thin-section electron microscopy. number of morphological and physiological These studies have established that the evidences for participation of individual JGA consists of the macula densa of the components of the JGA in the feedback distal renal tubule, the juxtaglomerular cells mechanism have been provided in previous (JGCs) in the media of the afferent arteriole studies. And, it is presumed that the GoCs and the Goormaghtigh cells (GoCs) to form must play an important role in controlling Send offprint request to: Dr. Sumie Kidokoro, Department of Anatomy, Yokohama City University School of Medicine, 3-9 Fukuura, Kanazawa, Yokohama, 236 Japan 393 394 S. Kidokoro the feedback mechanism as a functional and embeded in an Epon-Araldite mixture. center, because of their central position in For morphometric analysis of extent of the the JGA and coupling with gap junctions JGC layer in the afferent arteriole, semithick to other cellular compartments (Pricam sections (0.5 pm in thickness) were cut on a et al., '74; Boll et al., '75; Forssmann et al., Porter-Blum MT-1 ultramicrotome, mounted '77; Taugner et al ., '78; Spanidis et al., '82). on slide glasses in order, and stained with However, few reports dealing with the toluidine blue. Serial sections were obtained three-dimensional analysis of morphological from 40 glomeruli only in the subcapsular changes in the JGA under experimental regions of the renal cortex in each group, conditions have been presented . The present because the morphology of the JGA is study was carried out to observe changes known to vary depending on its location in the spatial relationship among the struc- in the kidney (Faarup, '65). Photomicro- tural components of the JGA after water graphs of these sections were taken at deprivation, because dehydration is known magnification of X 1,000. Extent of the JGC to cause elevation of plasma renin activity layer was calculated by the distance between (PRA) (Lucke et al., '80; Zucker et al., '82), the vascular pole and the distal end of JGC and this may accompany morphological layer along the central axis of the afferent changes in the JGA. arterioles reconstructed, because even when the number of JGCs was markedly dimin- Materials and Methods ished they are always found in the arteriolar wall at the vascular pole. To examine the Male Wistar rats ranging from 202 to 287 extent of the direct contact areas between g in body weight were fed with standard the GoC field and adjacent structural com- rat food pellets. They were divided into 4 ponents, reconstruction models were made groups of animals deprived water for 1, 2, 4 as follows: Electron micrographs of semi- and 7 days. Each group consists of 10 rats, serial sections obtained from every 10 thin and those treated without any experimental sections were taken at X 2,500 of the initial procedures were examined as control. Prior magnification, and printed to become to experimentation, blood pressure in X 7,500 in the final magnification. They individual animals was measured by the were traced on hard board of polyvinyl- tail-cuff method. Under pentobarbital anes- chloride, from which individual cellular thesia, the blood was collected from the compartments of the JGA (afferent arte- inferior vena cava of 5 animals in each group riole, distal renal tubule, GoC field and a to measure the plasma renin activity (PRA) part of glomerulus closely apposed to the by radioimmunoassay method (Fyhrquist vascular pole) were cut out and recon- et al., '76). In the other animals, the renal structed as shown in Figure 1. The contact tissue was fixed by perfusion with 2% areas were calculated using an Image Analyz- glutaraldehyde in 1M phosphate buffer ing System of the Model G/A Series (Muto following the method of Forssman et al. Kogyo Co. Ltd., Tokyo, Japan). ('77). The tissue blocks minced into 2x 1 x 2.5 mm were further fixed in the same Results fixative for 2 h, washed in buffer, and post- fixed in 0s04 in buffer for 45 min. They 1) Body weight and food intake: Water were then dehydrated with an ethanol deprivation caused a significant decrease in series, passed through propylene oxide, body weight and food intake (Table 1). JG Apparatus after Water Deprivation 395 Fig. 1. A model representing the three-dimensional structure of the juxtaglomerular apparatus (JGA) reconstructed from serial sections. A; afferent arteriole, D; distal renal tubule, E; efferent arteriole, GoC; Goormaghtigh cell (GoC) field (striped), SG; juxtaglomerular cell (JGC) area (dotted). Table 1. Alterations in body weight and food intake during water deprivation * The means of total volume of food taken by each animal during individual experimental periods. Decrease in average body weight was about after 2-day-dehydration, about 45% after 10% of the initial one after 1-day-water 4-day-dehydration, and about 36% after deprivation, about 15% after 2-day-dehydra- 7-day-dehydration, respectively. tion, about 20% after 4-day-dehydration, 2) Plasma renin activity (PRA): Average and more than 35% after 7-day-dehydration, values of PRA in individual cases were 15.25 respectively. In Table 1, food intake was ngAl/ml/h in control, 51.25 ngAl/ml/h indicated by the means of the total volume after 1-day-dehydration, 80 ngAl/ml/h after of food taken by each animal through 2-day-dehydration, and 112.5 ngAl/ml/h individual experimentations. It is obvious after 4-day-dehydration, respectively (Fig. that food intake per day decreased remark- 2). PRA after 7-day-water deprivation ably as the experimental period is prolonged. was not calculated, because body weight After one-day-dehydration, food intake was decreased so markedly that enough volume diminished to be 51.6% of control. In other of blood for radioimmunoassay was not experimental groups, it was about 53% obtained. However, PRA tended to rise 3 96 S. Kidokoro Fig. 2. Changes in blood pressure (BP) and plasma renin activity (PRA) during experiments. continuously throughout the experimental period and the value after 4-day-dehydration was about 7.4 times higher than in control (Fig. 2). 3) Extent of the juxtaglomerular cell (JGC) layer: JGCs were found only in the media of the afferent arteriole, and not found either in the efferent arteriole or in the extra- and intra-glomerular mesangial regions, as far as examined in this study. Extent of the JGC layer was 35.2±11.5 in control and significantly increased to be 53.1±16.4 p.m after 1-day-waterdeprivation (p<0.01). In the other experimental groups, 2-, 4-, and 7-day-dehydration, the values were 46.0±12.9 ,um, 423 ±17.4 ,um, and duration (day, ) 343±13 pm, respectively(Fig. 3). Fig, 3. Changes in extent of the JGCs in 4) Blood pressure: Averageblood pressure the afferent arterioles after water de- was 111 mm/Hg in control, 117 mm/Hg privation for various periods. The after 1-day-dehydration, 115.5 mm/Hg after vertical scale (length, Mm) indicates the dehydration for 2 days, 112 mm/Hg after distance between the JGC at the vascular pole and the distal end of JGC layer of 4-day-dehydration, and 108 mm/Hg after the afferent arteriole. JG Apparatus after Water Deprivation 397 7-day-dehydration, respectively (Fig. 2). at the vascular pole. Shape and route of One-day-dehydration group showed the the distal renal tubule passing by the JGA highest value, which is comparable to the showed a great variety. Some distal tubules changes in extent of JGC layer of the passed by the JGA without any contact afferent arteriole.