Granular Cells in the Juxtaglomerular Apparatus in Perinatal Rats Y. EGUCHI, MICHIKO YAMAKAWA, Y. MORIKAWA A N D Y. HASHIMOTO Department of Veterinary Anatomy, College o f Agriculture, University of Osaka Prefecture, Sakai City, Osaka 591, Japan
ABSTRACT
Granular cell indices (GCI; Dunihue and Robertson, '57) in kidneys of fetal and newborn rats were determined by examining sections stained with Bowie's technique. Some fetuses were delivered prematurely by Caesarean section a day earlier than the expected delivery, and were then nursed by a foster mother. Similarly, postmature Caesarean newborn rats were obtained; retention one day beyond the normal gestation was induced by maternal progesterone injections. The GCI was strikingly increased within a day after birth, followed by an immediate decrease thereafter. This was also observed in both premature and postmature newborn rats. It seems that this temporary increase of the GCI is not attributable solely to the age of rat, but follows only the separation from the maternal environment.
The juxtaglomerular apparatus (JGA) comprises three different groups of cells: (1) nongranular macula densa of the distal convoluted uriniferous tubule, (2) granular epithelioid JG cells of the afferent and efferent arterioles and (3) lacis cells, an alternate name of which is the extraglomerular mesangium (Barajas, ' 7 0 ) , located between the macula densa and the vascular pole of the glomerulus and granular intraglomerular mesangial cells. The lacis cells are continuous with the mesangial cells and may be transformed into JG cells in conditions of hyperactivity (Hartroft, '63). Furthermore, three-dimensional electron microscopic studies indicate an extensive constant contact between the distal tubule and both the extraglomerular mesangial region and efferent arteriole (Barajas, '70). JGA is believed to be associated with the storage and release of renin, a beginning enzyme for sequences leading to elevation of blood pressure. An increase in granules of JG cells probably indicates increased renin synthesis and decreased granularity probably indicates depressed activity (Hartrof t, '63). During the perinatal period, certain changes in function of the kidney and related changes in granules of JG cells are ANAT. Rm., 181: 627-634.
expected to occur in a newborn animal according to its separation from intrauterine circumstances. Nevertheless, only one report has been made on the perinatal mouse JGA by Kaylor and Carter ('67). Their results, however, were based on very few animals, showing a decrease in the glomerular cell index during the first two postnatal days. The present work was designed to clarify what changes, expressed as granular cell index (GCI) of Dunihue and Robertson ('57), would occur in the content of granular cells in the kidney during the perinatal period in the rat. MATERIALS AND METHODS
Rats of the Wistar strain were fed with a commercial diet (oriental pellets NMF) and water, both ad libitum. The day following an overnight mating was counted as the first day of gestation. Vaginal plugs were looked for. Vaginal smears were examined for the presence of sperm. The first series of animals comprised fetal rats on the nineteenth, twentieth, twenty-first and twenty-second days of gestation and newborn rats on the first, second, third and fifth days after birth. Spontaneous birth in our stock rats occurred Received M a y 13, '74. Accepted Aug. 19, '74.
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Y. EGUCHI, M. YAMAKAWA, Y. MORIKAWA AND Y. HASHIMOTO
approximately in the afternoon of the in groups, was recorded. The number of glomeruli having associated granular cells twenty-second day of gestation. The second series of animals consisted was divided by the total number of glomerof premature newborn rats obtained by uli. The divided value was multiplied by Caesarean section on the twenty-first day 100 to give the GCI. During this enumeraof gestation, one day earlier than the tion, only mature glomeruli, as judged by expected spontaneous delivery. In order size and vascularity, were counted; immato obtain vivid premature newborn rats ture glomeruli in the nephrogenic zone, quickly, the mothers were killed by de- which was present in every kidney obcapitation, and fetuses were removed from served, were not counted. Since the GCI the uterus by severance of the umbilical formed a percentage, angular (arcsine) cords and were allowed to breathe air. transformation of each GCI was performed These rats were nursed by foster mothers, in order to apply statistical analysis (Snedeeach mother having been deprived of all cor, '56). of her own young. As a means of encouragRESULTS ing a foster mother to accept Caesarean newborn rats, some of her urine was Fetuses and spontaneous painted onto the skins of all Caesarean newbcm rats newborn rats which were to be placed in Both the body weight and the kidney her nest, Only those rats in the nest with their stomachs full of milk a day and two weight were increased consistently from the nineteenth day of gestation to the fifth days later were used for gathering data. The third series of animals consisted of day after birth (table 1). Histologically, every kidney observed fetuses retained for one day beyond the normal gestation and one- and two-day- showed a nephrogenic zone with a width old postmature newborn rats obtained by that varied in the peripheral portion of the Caesarean section on the twenty-third organ. Under the nephrogenic zone, fully day of gestation. Prolonged gestation was formed glomeruli were scattered. Granuachieved by daily maternal subcutaneous lated cells were found in some glomeruli in injections of three mg progesterone in the deep cortical area. During the fetal sesame oil (Oophormin luteum, Teikoku period, granulated cells were very few Hormone Mfg. Co.) from the twentieth (one or two cells) in sections of a glomerthrough twenty-second days of gestation. ulus, and were exclusively located on the Postmature newborn rats were nursed by wall of arterioles (fig. 2). The GCI and it3 arcsine value were relatively low with n o foster mothers as well. At autopsy, the kidneys of fetuses and significant fluctuation during the fetal newborn rats were removed; the left kid- period (table 1 and fig. 1). On the first day after birth, the mean ney was quickly fixed in a fluid which had been made up by mixing 100 ml of 80% GCI was abruptly increased with a highly ethanol with one g of trichloroacetic acid significant rise of its arcsine value (P
ABSTRACT
Granular cell indices (GCI; Dunihue and Robertson, '57) in kidneys of fetal and newborn rats were determined by examining sections stained with Bowie's technique. Some fetuses were delivered prematurely by Caesarean section a day earlier than the expected delivery, and were then nursed by a foster mother. Similarly, postmature Caesarean newborn rats were obtained; retention one day beyond the normal gestation was induced by maternal progesterone injections. The GCI was strikingly increased within a day after birth, followed by an immediate decrease thereafter. This was also observed in both premature and postmature newborn rats. It seems that this temporary increase of the GCI is not attributable solely to the age of rat, but follows only the separation from the maternal environment.
The juxtaglomerular apparatus (JGA) comprises three different groups of cells: (1) nongranular macula densa of the distal convoluted uriniferous tubule, (2) granular epithelioid JG cells of the afferent and efferent arterioles and (3) lacis cells, an alternate name of which is the extraglomerular mesangium (Barajas, ' 7 0 ) , located between the macula densa and the vascular pole of the glomerulus and granular intraglomerular mesangial cells. The lacis cells are continuous with the mesangial cells and may be transformed into JG cells in conditions of hyperactivity (Hartroft, '63). Furthermore, three-dimensional electron microscopic studies indicate an extensive constant contact between the distal tubule and both the extraglomerular mesangial region and efferent arteriole (Barajas, '70). JGA is believed to be associated with the storage and release of renin, a beginning enzyme for sequences leading to elevation of blood pressure. An increase in granules of JG cells probably indicates increased renin synthesis and decreased granularity probably indicates depressed activity (Hartrof t, '63). During the perinatal period, certain changes in function of the kidney and related changes in granules of JG cells are ANAT. Rm., 181: 627-634.
expected to occur in a newborn animal according to its separation from intrauterine circumstances. Nevertheless, only one report has been made on the perinatal mouse JGA by Kaylor and Carter ('67). Their results, however, were based on very few animals, showing a decrease in the glomerular cell index during the first two postnatal days. The present work was designed to clarify what changes, expressed as granular cell index (GCI) of Dunihue and Robertson ('57), would occur in the content of granular cells in the kidney during the perinatal period in the rat. MATERIALS AND METHODS
Rats of the Wistar strain were fed with a commercial diet (oriental pellets NMF) and water, both ad libitum. The day following an overnight mating was counted as the first day of gestation. Vaginal plugs were looked for. Vaginal smears were examined for the presence of sperm. The first series of animals comprised fetal rats on the nineteenth, twentieth, twenty-first and twenty-second days of gestation and newborn rats on the first, second, third and fifth days after birth. Spontaneous birth in our stock rats occurred Received M a y 13, '74. Accepted Aug. 19, '74.
627
628
Y. EGUCHI, M. YAMAKAWA, Y. MORIKAWA AND Y. HASHIMOTO
approximately in the afternoon of the in groups, was recorded. The number of glomeruli having associated granular cells twenty-second day of gestation. The second series of animals consisted was divided by the total number of glomerof premature newborn rats obtained by uli. The divided value was multiplied by Caesarean section on the twenty-first day 100 to give the GCI. During this enumeraof gestation, one day earlier than the tion, only mature glomeruli, as judged by expected spontaneous delivery. In order size and vascularity, were counted; immato obtain vivid premature newborn rats ture glomeruli in the nephrogenic zone, quickly, the mothers were killed by de- which was present in every kidney obcapitation, and fetuses were removed from served, were not counted. Since the GCI the uterus by severance of the umbilical formed a percentage, angular (arcsine) cords and were allowed to breathe air. transformation of each GCI was performed These rats were nursed by foster mothers, in order to apply statistical analysis (Snedeeach mother having been deprived of all cor, '56). of her own young. As a means of encouragRESULTS ing a foster mother to accept Caesarean newborn rats, some of her urine was Fetuses and spontaneous painted onto the skins of all Caesarean newbcm rats newborn rats which were to be placed in Both the body weight and the kidney her nest, Only those rats in the nest with their stomachs full of milk a day and two weight were increased consistently from the nineteenth day of gestation to the fifth days later were used for gathering data. The third series of animals consisted of day after birth (table 1). Histologically, every kidney observed fetuses retained for one day beyond the normal gestation and one- and two-day- showed a nephrogenic zone with a width old postmature newborn rats obtained by that varied in the peripheral portion of the Caesarean section on the twenty-third organ. Under the nephrogenic zone, fully day of gestation. Prolonged gestation was formed glomeruli were scattered. Granuachieved by daily maternal subcutaneous lated cells were found in some glomeruli in injections of three mg progesterone in the deep cortical area. During the fetal sesame oil (Oophormin luteum, Teikoku period, granulated cells were very few Hormone Mfg. Co.) from the twentieth (one or two cells) in sections of a glomerthrough twenty-second days of gestation. ulus, and were exclusively located on the Postmature newborn rats were nursed by wall of arterioles (fig. 2). The GCI and it3 arcsine value were relatively low with n o foster mothers as well. At autopsy, the kidneys of fetuses and significant fluctuation during the fetal newborn rats were removed; the left kid- period (table 1 and fig. 1). On the first day after birth, the mean ney was quickly fixed in a fluid which had been made up by mixing 100 ml of 80% GCI was abruptly increased with a highly ethanol with one g of trichloroacetic acid significant rise of its arcsine value (P
