STUDIES CONCERNING THE SITE OF RENIN FORMATION IN THE KIDNEY : III. THE APPARENT SITE OF RENIN FORMATION IN THE TUBULES OF THE MESONEPHROS AND METANEPHROS OF THE HOG FETUS

STUDIES CONCERNING THE SITE OF RENIN FORMATION IN THE KIDNEY : IV. THE RENIN CONTENT OF THE MAMMALIAN KIDNEY FOLLOWING SPECIFIC NECROSIS OF PROXIMAL CONVOLUTED TUBULAR EPITHELIUM

1. The administration of tartrate to adult rabbits was found to produce in some of them, a profound and widespread necrosis of the proximal convoluted tubular epithelium without affecting the other portions of the nephrons. 2. The markedly damaged kidneys were found to be almost completely devoid of pressor substance (renin), indicating that in the mammalian kidney, the epithelium of the proximal convoluted tubules is concerned in the formation or storage of renin.

Ontogeny of pulmonary and renal angiotensin-converting enzyme in pigs

The present study investigated the ontogeny of pulmonary and renal angiotensin-converting enzyme (ACE) in foetal and postnatal pigs, and examined the effect of cortisol on tissue ACE in utero. Data were compared with those in sheep at similar ages. Under anaesthesia, tissues and umbilical blood were collected from pig foetuses between 81-115 days of gestation (term, 115+/-2 days). Twelve foetuses delivered at 97+/-2 days were infused with saline or cortisol (3-6 mgkg(-1)day(-1)) using osmotic mini-pumps implanted 6 days previously. Tissues were collected from newborn piglets, and from pigs at 2-4 weeks, 10-12 weeks and 10-12 months of age. Unlike in sheep, gestational age and exogenous cortisol had no effect on pulmonary or renal ACE in pigs. After birth, pulmonary ACE decreased to a nadir at 2-4 weeks and remained low thereafter. Renal ACE increased between 10-12 weeks and 10-12 months. Postnatal changes in tissue ACE may have consequences for cardiovascular, pulmonary and renal function in pigs.

Ontogeny of renin immunoreactive cells in the human kidney

We studied the time of appearance of renin-immunoreactive cells in prenatal human kidneys by immunohistochemistry and transmission electron microscopy (TEM). Renin immunoreactivity was detectable as early as the 5th or 6th gestational week in the mesonephros and appeared at 8 weeks of gestation in the metanephros. In a 8 week old embryo "renin granules" were seen by TEM in the juxtaglomerular epithelioid granular cells of metanephric tissue. In the embryos delivered by prostaglandin-induced abortion, granular renin immunoreactivity was also present in the cells of the proximal convoluted tubule. Our results support the contention that the renin-angio-tension system is active during fetal life and indicates a role for renin even during the embryonic period. In addition, they document a morphologically detectable effect of prostaglandins on the distribution of renin in the kidney.

Mesonephric excretory function related to its influence on differentiation of fetal gonads

The mammalian intermediate fetal kidney, the mesonephros, is known in different species to excrete body waste products during a limited period of fetal life. Recently, the mesonephros and its derivatives have been shown to influence gonadal functions in several ways. Thus, the mesonephric cells are responsible for regulating the onset of meiosis in different mammals by the secretion of two substances, a meiosis-inducing substance (MIS) and a meiosis-preventing substance (MPS). In this paper, the relation between mesonephric kidney function and its influence on the gonads is reviewed through literature studies. It seems that cessation of mesonephric excretion precedes onset of meiosis in the ovary in different species. It is suggested that the mesonephric renal function interferes with synthesis and/or secretion of MIS or that the excreted products may interfere with the responsiveness to MIS of the germ cells.

Renin immunohistochemistry in the mesonephros and metanephros of the pig embryo

The occurrence and distribution of renin was investigated in meso- and metanephric kidneys of pig embryos in various gestational stages. The immunohistochemical peroxidase-antiperoxidase-method (PAP) was used on paraffin sections after application of an antiserum against mouse renin which cross reacts with pig renin. Renin immunoreactivity was already found in the mesonephros of 21 day pig embryos (crown-rump(CR)-length 12 mm) with the strongest reaction in the media of the juxtaglomerular afferent arteriole. Efferent vessels, mesonephric arteries, and the aortic wall also contained scattered renin-positive cells. In the definitive kidney, renin was not detected prior to the 25 mm CR-length-stage. In 45 mm embryos, immunocytochemical staining was observed not only in the media of kidney arteries and arterioles, but also in proximal tubules after pinocytic absorption of filtered renin. TEM-studies revealed that the media of both the mesonephric and the developing metanephric arteries and arterioles contains epithelioid cells whose ultrastructure is very similar to that of renin-producing cells in the adult organ. The observed distribution of renin-producing cells along the entire renal arterial tree points to the possibility that the major function of the renin-angiotensin system in the fetal animal is to participate in the stabilization of renal perfusion pressure.

The effects of gestational age and chronic fetal decapitation on arterial blood pressure in the pig fetus

Blood pressure was measured in anaesthetized pig fetuses decapitated at 40-43 days of gestation and in intact fetuses between 35 and 112 days of gestation (term is 114 days). In the intact fetuses arterial blood pressure increased significantly from 0.8 +/- 0.1 kPa (mean +/- SEM) at 35 days to 5.8 +/- 0.2 kPa at 112 days (P less than 0.05). The arterial blood pressure of decapitated fetuses was similar to that of intact fetuses at 70 days of gestation (2.7 +/- 0.4 kPa vs. 2.5 +/- 0.1 kPa, respectively) but did not change with increasing gestational age thereafter. Hence in late gestation (greater than 90-100 days) the arterial blood pressure of the decapitated fetuses was significantly less than that of intact fetuses (P less than 0.05). These observations demonstrate that the control of blood pressure in the pig varies with gestational age and suggest that the developmental changes occurring after about 100 days gestation require tissues within the head.

A study of factors affecting blood pressure and angiotensin II in newborn infants

Blood pressure has been measured using the Doppler ultrasonic technique in 144 infants in the first 11 days of life. Venous angiotensin II levels measured by radioimmunoassay were determined in 75 of these babies. Highly significant correlations were found between systolic blood pressure and gestational age and body weight. AII was inversely related to blood pressure and significantly related to birth weight. Babies with respiratory distress were found to be significantly hypotensive and to have markedly raised AII levels.

Characterization of the renin-antirenin system

Rabbit antibody capable of neutralizing the pressor activity of the enzyme renin, derived from hog kidneys, was characterized with respect to type and capacity to react serologically. Three antirenin antibodies were detected, both a precipitating and nonprecipitating, neutralizing antibody as well as a neutralizing antibody capable of being absorbed by inactivated renin. The precipitating, neutralizing antibody was purified and used successfully in an assay for hog renin by means of a hemagglutination inhibition test. By immunofluorescent methods utilizing the purified antiserum, renin was found to be localized in the macula densa of the distal convoluted tubules and the juxtaglomerular cells of the afferent arteriole in both hog and dog kidneys.