Multinuclear NMR studies of intracellular cations in perfused hypertensive rat kidney.

We have investigated hypertension-associated alterations in intracellular cations in the kidney by measuring intracellular pH, free Mg2+, free Ca2+, and Na+ concentrations in perfused normotensive and hypertensive rat (8-14 weeks old) kidneys using 31P, 19F, and double quantum-filtered (DQ) 23Na NMR. The effects of both anoxia and ischemia on the 23Na DQ signal confirmed its ability to detect changes in intracellular Na+. However, there was a sizable contribution of the extracellular Na+ to the 23Na DQ signal of the kidney. The intracellular free Ca2+ concentration, measured using 19F NMR and 5,5'difluoro-1,2-bis(2-aminophenoxy)ethane N,N,N',N'-tetraacetic acid, also increased dramatically during ischemia; the increase could be partly reversed by reperfusion. No significant differences were found between normotensive and hypertensive kidneys in the ATP level, intracellular pH, intracellular free Mg2+, and the 23Na DQ signal or in the extent of the extracellular contribution to the 23Na DQ signal. Oxygen consumption rates were also similar for the normotensive (5.02 +/- 0.46 mumol of O2/min/g) and hypertensive (5.47 +/- 0.42 mumol O2/min/g) rat kidneys. The absence of a significant difference in intracellular pH, Na+ concentration, and oxygen consumption between normotensive and hypertensive rat kidneys suggests that an alteration in the luminal Na+/H+ antiport activity in hypertension is unlikely. However, a highly significant increase (64%, p less than 0.01) in free Ca2+ concentration was found in perfused kidneys from hypertensive rats (557 +/- 48 nM, blood pressure = 199 +/- 5 mmHg, n = 6) compared with normotensive rats (339 +/- 21 nM, blood pressure = 134 +/- 6, n = 4) indicating altered renal calcium homeostasis in essential hypertension. An increase in intracellular free Ca2+ concentration without an accompanying change in the intracellular Na+ suggests, among many possibilities, that the Ca2+/Mg(2+)-ATPase may be inhibited in the hypertensive renal tissue.     

ACE2 and ANG-(1-7) in the rat uterus during early and late gestation

The present study was designed to determine ANG peptide content [ANG I, ANG II, ANG-(1-7)], ACE2 mRNA, and the immunocytochemical distribution of ANG-(1-7) and ACE2 in the uteroembryonic unit during early and late gestation in Sprague-Dawley rats and in a rat model of pregnancy-induced hypertension, the reduced uterine perfusion pressure (RUPP) model. At early pregnancy ANG-(1-7) and ACE2 staining were localized in the primary and secondary decidual zone and luminal and glandular epithelial cells. During late gestation, ANG-(1-7) and ACE2 staining was visualized in the labyrinth placenta and amniotic and yolk sac epithelium. Uterine ANG II concentration at early pregnancy was significantly decreased by 21-55% in the implantation and interimplantation sites compared with virgin rats, whereas ANG-(1-7) levels were maintained at prepregnancy levels. At late gestation, uterine concentrations of ANG I and ANG II were significantly increased (30% and 25%, respectively). In RUPP animals, ANG-(1-7) concentration is significantly reduced in the uterus (181 +/- 16 vs. 372 +/- 74 fmol/g of tissue) and placenta (143 +/- 26 vs. 197 +/- 20 fmol/g of tissue). ACE2 mRNA increased in the uterus of early pregnant compared with virgin rats, yet within the implantation site it was downregulated. At late pregnancy, ACE2 mRNA is elevated by 58% in the uterus and decreased by 59% in RUPP animals. The regulation of ANG-(1-7) and ACE2 in early and late pregnancy supports the hypothesis that ANG-(1-7) and ACE2 may act as a local autocrine/paracrine regulator throughout pregnancy, participating in the early (angiogenesis, apoptosis, and growth) and late (uteroplacental blood flow) events of pregnancy.     

Ouabain-sensitive and -insensitive ATPase activities in the kidney and the liver of spontaneously hypertensive rats.

Ouabain-sensitive and-insensitive ATPase activities were measured in the kidneys and the kidneys and the liver of male and female rats of the Lyon hypertensive (LHS) and Lyon normotensive strain (LNS). At the age of 48 +/- 2 weeks, hypertensive rats exhibited a significantly higher blood pressure and body weight than age-matched normotensive rats. Ouabian-insensitive ATPase activity was decreased in the kidney, but not in the liver of hypertensive rats compared to normotensive rats. Ouabian-sensitive ATPase activity was non significantly decreased in the kidney of hypertensive rats.     

Captopril normalises systolic blood pressure in rats with hypertension induced by fetal exposure to maternal low protein diets

Recent studies have demonstrated that the feeding of low protein diets to rats during pregnancy induces hypertension in their offspring. Maternal-diet-induced hypertension has been previously associated with elevated pulmonary angiotensin converting enzyme (ACE) activity. In the present study, the importance of the renin angiotensin system, and in particular ACE, in the maintenance of the hypertensive state, is investigated. Pulmonary and plasma ACE activity were determined in rats of different ages, following in utero exposure to 18 (control) or 9% (deficient) casein diets. No maternal diet induced changes in pulmonary ACE were noted, but at 4 and 13 weeks of age, plasma ACE activity was increased by 34 and 134%, respectively in 9% casein exposed rats relative to controls (P<0.001). Thirteen-week-old rats had significantly raised systolic blood pressure (28 mmHg, P<00.05), and tended to have higher diastolic blood pressure (not significant). These hypertensive animals had slightly raised plasma angiotensin II concentrations (30% higher, not significant), but similar renin activities, when compared with normotensive controls. Treatment of normotensive and hypertensive rats with the ACE inhibitor captopril demonstrated that higher plasma ACE activity may play a major role in the maintenance of maternal-diet-induced hypertension. Whilst normotensive rats showed no significant response to drug treatment, systolic blood pressure in the hypertensive rats fell rapidly to the level observed in the normotensive control group. Blood pressure remained at this lower level until treatment was withdrawn, at which time pressure began to increase slowly, but steadily. A period of 7–8 weeks was required following cessation of captopril administration for the restoration of hypertension.The data are consistent with the hypothesis that components of the renin-angiotensin system, and in particular plasma ACE, are involved in the maintenance of maternal-diet-induced hypertension.     

Effect of estrogen on neprilysin expression in uterus and kidney of Sprague-Dawley normotensive and heterozygous (mRen2)27-transgenic hypertensive rats

The present study was designed to determine whether estrogen modulates the angiotensin processing enzymes in membrane homogenates obtained from uterus and kidney cortex and medulla of Sprague-Dawley (SD) and heterozygous (mRen2)27-transgenic hypertensive (Tg(+)) female rats treated with or without 17beta-estradiol (E2). We evaluated estrogen's influence on neprilysin (NEP), an endopeptidase that forms angiotensin-(1-7) [Ang-(1-7)] and on aminopeptidase (AMP), which degrades Ang-(1-7). Renal tissue from normotensive and hypertensive male rats was also evaluated. E2 up-regulated NEP mRNA in the uterus of both SD and Tg(+) and this was associated with increased NEP activity in the uterus of SD (0.31+/-0.03 nmol/min/mg versus 0.18+/-0.04 nmol/min/mg of protein, p<0.05) and Tg(+) (0.26+/-0.04 nmol/min/mg versus 0.13+/-0.02 nmol/min/mg of protein, p<0.05) female). E2 had no significant effect on NEP activity in cortex and medulla of hypertensive and normotensive female. In female animals, cortical NEP activity is two-fold higher than medullary; in males there is a four-fold higher cortical NEP activity as compared to medulla. In male animals, medullary NEP was significantly lower than females with or without E2 treatment; no gender specific effect was found in cortex. E2 treatment also caused a two-fold increase in AMP activity in the uterus and 1.6-fold decrease in kidney cortex of SD and Tg(+) female (p<0.05). Our studies indicate that NEP may be a primary candidate for increased Ang-(1-7) processing in the uterus with estrogen treatment; kidney NEP, on the other hand, showed no modulation by estrogen, suggesting that down regulation of other processing enzymes, like AMP and ACE, may come into play in the kidney with estrogen replacement. In addition, these studies showed that there is tissue-specific regulation of NEP with estrogen treatment that is strain independent.     

Temporal-spatial expression of ANG-(1-7) and angiotensin-converting enzyme 2 in the kidney of normal and hypertensive pregnant rats

We recently demonstrated that renin-angiotensin system (RAS) overactivity during late gestation in rats is associated with increased kidney and urine levels of ANG-(1-7) and enhanced kidney immunostaining of ANG-(1-7) and angiotensin-converting enzyme 2 (ACE2). To understand the temporal-spatial changes in normal and hypertensive pregnancies, the renal distribution of ANG-(1-7) and ACE2 in association with kidney angiotensin peptides and ACE2 activity was examined in virgin, normal pregnant (NP; gestational days 5, 15, and 19) and reduced uterine perfusion pressure (RUPP at day 19) pregnant Sprague-Dawley rats. ANG-(1-7) and ACE2 immunocytochemical staining increased 1.8- and 1.9-fold and 1.7- and 1.8-fold, respectively, at days 15 and 19 of NP, compared with virgin rats. ANG-(1-7) and ANG II concentrations were increased in the kidney at 19 days of gestation. ACE2 activity measured using a fluorescent substrate was increased 1.9- and 1.9-fold in the cortex and 1.9- and 1.8-fold in the medulla at days 15 and 19 of NP. In the RUPP animals, ANG-(1-7) immunostaining and concentration were significantly decreased compared with 19-day NP rats. ACE2 activity was unchanged in the cortex and medulla of RUPP rats. In conclusion, during NP, the concurrent changes of ACE2 and ANG-(1-7) suggest that ACE2 plays an important role in regulating the renal levels of ANG-(1-7) at mid to late gestation. However, the decrease in renal ANG-(1-7) content in the absence of a concomitant decrease in ACE2 implicates the participation of other ANG-(1-7) forming or degrading enzymes during hypertensive pregnancy.     

Feeding blueberry diets inhibits angiotensin II-converting enzyme (ACE) activity in spontaneously hypertensive stroke-prone rats

Feeding flavonoid-rich blueberries to spontaneously hypertensive stroke-prone rats (SHRSP) lowers blood pressure. To determine whether this is due to inhibition of angiotensin-converting enzyme (ACE) activity, as seen with other flavanoid-rich foods, we fed blueberries to SHRSP and normotensive rats and analyzed ACE activity in blood and tissues. After 2 weeks on a control diet, the hypertensive rats showed 56% higher levels of ACE activity in blood as compared with the normotensive rats (p < 0.05). Feeding a 3% blueberry diet for 2 weeks lowered ACE activity in the SHRSP (p < 0.05) but not the normotensive rats. ACE activity in plasma of SHRSP was no longer elevated at weeks 4 and 6, but blueberry feeding inhibited ACE in SHRSP after 6 weeks. Blueberry diets had no effect on ACE activity in lung, testis, kidney, or aorta. Our results suggest that dietary blueberries may be effective in managing early stages of hypertension, partially due to an inhibition of soluble ACE activity.     

Sex differences in the lung ACE/ACE2 balance in hypertensive rats

The angiotensin-converting enzyme (ACE)/Angiotensin II (Ang II) and angiotensin-converting enzyme 2 (ACE2)/angiotensin-(1-7) (Ang-(1-7)) pathways are coexpressed in most tissues. The balance between these pathways determines, at least in part, whether tissue damage will occur in response to pathological stimuli. The present study tested the hypothesis that male sex and high blood pressure are associated with ACE/ACE2 imbalance in the lungs. Experiments were conducted in male and female Wistar rats and spontaneously hypertensive rats (SHRs). Lung ACE and ACE2 gene expression was also evaluated in normotensive and hypertensive humans using the Genotype-Tissue Expression (GTEx) project. Compared with Wistar rats and female SHRs, male SHRs displayed reduced lung ACE2 mRNA, ACE2 protein abundance and ACE2 activity, and increased Ang II concentration. Lung ACE mRNA levels were higher in male SHRs than in Wistar rats, whereas lung ACE protein abundance and activity were similar among the four groups of rats. Lung Ang-(1-7) concentration was higher in female than in male SHRs (89 ± 17 vs. 43 ± 2 pg/g, P<0.05). Lung ACE to ACE2 mRNA expression in hypertensive patients was significantly higher than that in normotensive subjects. Taken together, these results demonstrate that male hypertensive rats display imbalance between the ACE/Ang II and ACE2/Ang-(1-7) pathways in the lungs mainly attributable to ACE2 down-regulation. Further studies should be conducted to investigate whether this imbalance between ACE/ACE2 may promote and accelerate lung injury in respiratory infections, including coronavirus disease 2019 (COVID-19).     

Reciprocal changes in renal ACE/ANG II and ACE2/ANG 1-7 are associated with enhanced collecting duct renin in Goldblatt hypertensive rats

Alterations in the balance between ANG II/ACE and ANG 1-7/ACE2 in ANG II-dependent hypertension could reduce the generation of ANG 1-7 and contribute further to increased intrarenal ANG II. Upregulation of collecting duct (CD) renin may lead to increased ANG II formation during ANG II-dependent hypertension, thus contributing to this imbalance. We measured ANG I, ANG II, and ANG 1-7 contents, angiotensin-converting enzyme (ACE) and ACE2 gene expression, and renin activity in the renal cortex and medulla in the clipped kidneys (CK) and nonclipped kidneys (NCK) of 2K1C rats. After 3 wk of unilateral renal clipping, systolic blood pressure and plasma renin activity increased in 2K1C rats (n = 11) compared with sham rats (n = 9). Renal medullary angiotensin peptide levels were increased in 2K1C rats [ANG I: (CK = 171 ± 4; NCK = 251 ± 8 vs. sham = 55 ± 3 pg/g protein; P < 0.05); ANG II: (CK = 558 ± 79; NCK = 328 ± 18 vs. sham = 94 ± 7 pg/g protein; P < 0.001)]; and ANG 1-7 levels decreased (CK = 18 ± 2; NCK = 19 ± 2 pg/g vs. sham = 63 ± 10 pg/g; P < 0.001). In renal medullas of both kidneys of 2K1C rats, ACE mRNA levels and activity increased but ACE2 decreased. In further studies, we compared renal ACE and ACE2 mRNA levels and their activities from chronic ANG II-infused (n = 6) and sham-operated rats (n = 5). Although the ACE mRNA levels did not differ between ANG II rats and sham rats, the ANG II rats exhibited greater ACE activity and reduced ACE2 mRNA levels and activity. Renal medullary renin activity was similar in the CK and NCK of 2K1C rats but higher compared with sham. Thus, the differential regulation of ACE and ACE2 along with the upregulation of CD renin in both the CK and NCK in 2K1C hypertensive rats indicates that they are independent of perfusion pressure and contribute to the altered content of intrarenal ANG II and ANG 1-7.     

Stanniocalcin (STC) in the endometrial glands of the ovine uterus: regulation by progesterone and placental hormones

Stanniocalcin (STC) is a hormone in fish that regulates calcium levels. Mammals have two orthologs of STC with roles in calcium and phosphate metabolism and perhaps cell differentiation. In the kidney and gut, STC regulates calcium and phosphate homeostasis. In the mouse uterus, Stc1 increases in the mesometrial decidua during implantation. These studies determined the effects of pregnancy and related hormones on STC expression in the ovine uterus. In Days 10-16 cyclic and pregnant ewes, STC1 mRNA was not detected in the uterus. Intriguingly, STC1 mRNA appeared on Day 18 of pregnancy, specifically in the endometrial glands, increased from Day 18 to Day 80, and remained abundant to Day 120 of gestation. STC1 mRNA was not detected in the placenta, whereas STC2 mRNA was detected at low abundance in conceptus trophectoderm and endometrial glands during later pregnancy. Immunoreactive STC1 protein was detected predominantly in the endometrial glands after Day 16 of pregnancy and in areolae that transport uterine gland secretions across the placenta. In ovariectomized ewes, long-term progesterone therapy induced STC1 mRNA. Although interferon tau had no effect on endometrial STC1, intrauterine infusions of ovine placental lactogen (PL) increased endometrial gland STC1 mRNA abundance in progestinized ewes. These studies demonstrate that STC1 is induced by progesterone and increased by a placental hormone (PL) in endometrial glands of the ovine uterus during conceptus (embryo/fetus and extraembryonic membranes) implantation and placentation. Western blot analyses revealed the presence of a 25-kDa STC1 protein in the endometrium, uterine luminal fluid, and allantoic fluid. The data suggest that STC1 secreted by the endometrial glands is transported into the fetal circulation and allantoic fluid, where it is hypothesized to regulate growth and differentiation of the fetus and placenta, by placental areolae.     

The lack of cardiac hypertrophy in newborn Prague hypertensive rats.

Newborn rats of four different strains with spontaneous hypertension show heart enlargement mainly due to cardiac hyperplasia. To determine whether this anomaly is common in all genetically hypertensive rats, we have compared newborns of Prague hypertensive rats (PHR) with their respective normotensive controls (PNR). The heart ventricles, kidneys and livers of newborn animals were analyzed for their weight, protein and DNA content. The total heart weight and the heart/body weight ratio were significantly lower in PHR than in PNR. On the other hand, there were no differences in total or relative kidney weight and in total liver weight. The relative protein content was significantly lower in kidney and liver of PHR but there were no differences between hypertensive and normotensive animals in relative DNA content of all organs studied. Our results suggest a possible dissociation of genes which determine organ weights from those responsible for blood pressure determination.     

Effect of angiotensin II blockade on a new congenic model of hypertension derived from transgenic Ren-2 rats

The generation of the Lew.Tg(mRen2) congenic hypertensive rat strain, developed through a backcross of the hypertensive (mRen2)27 transgenic rat with normotensive Lewis rats, provides a new model by which primary hypertension can be studied without the genetic variability found in the original strain. The purpose of this study was to characterize the Lew.Tg(mRen2) rats by dually investigating the effects of type 1 angiotensin II (ANG II) receptor (AT(1)) blockade and angiotensin-converting enzyme (ACE) activity inhibition on the ANG-(1-7)/ACE2 axis of the renin-angiotensin system in this new hypertensive model. The control of blood pressure elicited by 12-day administration of either lisinopril (mean difference change = 92 +/- 2, P < 0.05) or losartan (mean difference change = 69 +/- 2, P < 0.05) was associated with 54% and 33% increases in cardiac ACE2 mRNA and 54% and 43% increases in cardiac ACE mRNA, respectively. Lisinopril induced a 3.1-fold (P < 0.05) increase in renal cortical expression of ACE2, whereas losartan increased ACE2 mRNA 3.5-fold (P < 0.05). Both treatment regimens increased renal ACE mRNA 2.6-fold (P < 0.05). The two therapies augmented ACE2 protein activity, as well as increased cardiac and renal AT(1) receptor mRNAs. ACE inhibition reduced plasma ANG II levels (81%, P < 0.05) and increased plasma ANG-(1-7) (265%, P < 0.05), whereas losartan had no effect on the peptides. In contrast with what had been shown in normotensive rats, ACE inhibition decreased renal ANG II excretion and transiently decreased ANG-(1-7) excretion, whereas losartan treatment was associated with a consistent decrease in ANG-(1-7) urinary excretion rates. In response to the treatments, the expression of both renal cortical renin and angiotensinogen mRNAs was significantly augmented. The paradoxical effects of blockade of ANG II synthesis and activity on urinary excretion rates of the peptides and plasma angiotensins levels suggest that, in Lew.Tg(mRen2) congenic rats, a failure of compensatory ACE2 and ANG-(1-7)-dependent vasodepressor mechanisms may contribute both to the development and progression of hypertension driven by increased formation of endogenous ANG II.     

Study of antihypertensive mechanism of Tribulus terrestris in 2K1C hypertensive rats: role of tissue ACE activity

Tribulus terrestris is a natural herb used for treating many diseases including hypertension. According to previous reports, aqueous extract of tribulus fruits may have some antihypertensive effect with an unknown mechanism. The present study investigated the antihypertensive mechanism of tribulus in 2K1C hypertensive rats by measurement of circulatory and local ACE activity in aorta, heart, kidney and lung. Four groups of rats were selected; control, sham, operated or hypertensive and tribulus treated hypertensive group. Hypertension was induced using silver clip on renal artery by surgery. Four weeks after surgery, a single daily dose of 10 mg/kg of lyophilized aqueous extract of tribulus fruit were given orally to 2K1C rats for four weeks. ACE activity was determined by high performance liquid chromatography (HPLC). Blood pressure was measured by the tail-cuff method. The systolic blood pressure (SBP) was significantly increased in 2K1C rats compared to control rats. The SBP of tribulus fed hypertensive rats was significantly decreased compared to hypertensive rats. The ACE activity in all tissues of 2K1C rats including: aorta, heart, kidney, lung as well as serum were significantly increased compared to normal rats. The ACE activity in all tissues of tribulus fed hypertensive rats was significantly lower than that of hypertensive rats, which was more pronounced in kidney. These results indicated that there is a negative correlation between consumption of tribulus and ACE activity in serum and different tissues in 2K1C rats.     

Chronobiologic Evaluation of Angiotensin-Converting Enzyme Activity in Serum and Lung Tissue from Normotensive and Spontaneously Hypertensive Rats

Angiotensin-converting enzyme (ACE) activity in serum and lung tissue from both normotensive Wistar-Kyoto (WKY) and spontaneously hypertensive rats (SHR) was determined at six different circadian times. In WKY rats serum ACE varied significantly within 24 h, mainly due to reduced enzyme activity at 12:00 h. In SHR the 24-h profile of serum ACE did not exhibit time-dependent differences. Mean serum ACE activity over 24 h was significantly higher in WKY than in SHR. In lung tissue ACE activity did not depend on the circadian time in either strain. Mean enzyme activity in lung tissue was not different between WKY and SHR. We conclude that circadian changes in the activity of serum and tissue ACE are unlikely to play an important role in the regulation of the circadian blood pressure profile in both normotensive and spontaneously hypertensive rats.     

Chronobiologic Evaluation of Angiotensin-Converting Enzyme Activity in Serum and Lung Tissue from Normotensive and Spontaneously Hypertensive Rats

Angiotensin-converting enzyme (ACE) activity in serum and lung tissue from both normotensive Wistar-Kyoto (WKY) and spontaneously hypertensive rats (SHR) was determined at six different circadian times. In WKY rats serum ACE varied significantly within 24 h, mainly due to reduced enzyme activity at 12:00 h. In SHR the 24-h profile of serum ACE did not exhibit time-dependent differences. Mean serum ACE activity over 24 h was significantly higher in WKY than in SHR. In lung tissue ACE activity did not depend on the circadian time in either strain. Mean enzyme activity in lung tissue was not different between WKY and SHR. We conclude that circadian changes in the activity of serum and tissue ACE are unlikely to play an important role in the regulation of the circadian blood pressure profile in both normotensive and spontaneously hypertensive rats.     

Maternal protein restriction reduces expression of angiotensin I-converting enzyme 2 in rat placental labyrinth zone in late pregnancy

Both the systemic and the uteroplacental renin-angiotensin system (RAS) display dramatic changes during pregnancy. However, whether gestational protein insufficiency affects the expressions of RAS in the placenta remains unknown. In this study, we hypothesized that the expression of Ace2 in the placental labyrinth was reduced by maternal protein restriction. Pregnant Sprague-Dawley rats were fed a normal diet or a low-protein diet (LP) from Day 1 of pregnancy until they were killed at Day 14 or Day 18. The labyrinth zone (LZ) of the placenta was then dissected and snap frozen for expression analysis by quantitative real-time PCR of Ace, Ace2, Agtr1a, Agtr1b, and Agtr2. Formalin-fixed placentas were used for immunohistochemical analysis on ACE and ACE2 proteins. The findings include 1) the expression of Ace2 in rat LZ was reduced by maternal protein restriction in late pregnancy; 2) ACE protein was mainly present in syncytiotrophoblasts, whereas ACE2 protein was found predominantly in fetal mesenchymal tissue and fetal capillaries; 3) Agtr1a was predominant in the rat LZ, and its mRNA levels, but not protein levels, were reduced by LP; 4) expressions of Ace, Ace2, and Agtr1a in the rat LZ and their response to LP occurred in a gender-dependent manner. These results may indicate that a reduced expression of Ace2 and perhaps an associated reduction in angiotensin (1-7) production in the placenta by maternal protein restriction may be responsible for fetal growth restriction and associated programming of adulthood hypertension.     

The human placenta as a target tissue for glucagon

Glucagon's effect on the placenta was studied in cultured human term trophoblast and in homogenized term and first-trimester placentas. In studies with cultured term trophoblast, glucagon stimulated the generation of cyclic AMP and estradiol secretion and inhibited placental lactogen secretion. Incubation of homogenates of term and of first-trimester placenta with 0.5 mM dibutyryl cAMP revealed a marked decrease of pyruvate kinase activity. Glucagon produced a similar decrease in first-trimester homogenates, but failed to affect term placentas. The present demonstration of the placenta as a target tissue for glucagon suggests an active contribution of the trophoblast to energy metabolism during pregnancy.     

Alteration in sialidase and other glycosidase activities in the kidney of spontaneously hypertensive rats: persistence after preventive treatment with hydralazine

Because kidney microangiopathy with capillary basement membrane thickening has been reported in spontaneous hypertension, we have studied the activities of three lysosomal glycosidases able to degrade the carbohydrate moieties of basement membrane constituents in the kidney cortex of 12-week-old spontaneously hypertensive rats (SHR) and age-matched normotensive Wistar Kyoto rats (WKY). These activities were also determined in SHR and WKY treated from 6 to 12 weeks of age with hydralazine (mean dose, 18 mg/kg per day in drinking water). Sialidase specific activity on sialyl-alpha 2-3-[3H]lactitol was markedly decreased in the kidney of untreated SHR, 40% activity remaining relative to that found in untreated age-matched WKY (p less than 0.001). beta-Galactosidase specific activity on p-nitrophenyl-beta-D-galactoside was also decreased, 86% activity remaining relative to that found in untreated WKY (p less than 0.001). Glucosyl-galactosyl-hydroxylysyl glucohydrolase specific activity on glucosyl-galactosyl-hydroxylysine was equally diminished, 74% activity remaining relative to that found in untreated age-matched WKY (p less than 0.001). In contrast, the activities of two control glycosidases inactive on the carbohydrate moieties of basement membrane constituents, alpha-glucosidase assayed with p-nitrophenyl-alpha-D-glucoside as substrate and beta-glucosidase assayed with p-nitrophenyl-beta-D-glucoside as substrate, were significantly increased. All the alterations in enzyme activities observed in the kidney of SHR were also present in the long-term treated normotensive SHR. No effect of the hydralazine treatment on the three enzyme activities investigated could be demonstrated in the WKY. Thus the alterations observed in the kidneys of SHR appear to be independent of blood pressure level.     

Effect of ACE inhibition on the fetal kidney: decreased renal blood flow.

The kidneys of nine fetuses whose mothers were chronically hypertensive were examined microscopically. Three of these mothers used antihypertensive agents throughout pregnancy including one who used an angiotensin-converting enzyme (ACE) inhibitor. The tubular defects found in these kidneys were compared to the kidneys of 20 normal controls, 13 fetuses with various multiple malformation syndromes and six cases of the twin to twin transfusion syndrome. Evidence from these cases as well as the literature suggest that the primary mechanism by which ACE inhibitors affect development of the fetal kidney is through decreased renal blood flow.