Common variants of the G protein-coupled receptor type 4 are associated with human essential hypertension and predict the blood pressure response to angiotensin receptor blockade.

Non-synonymous GRK4 variants, R65L, A142V and A486V, are associated with essential hypertension in diverse populations. This study replicated the association of GRK4 variants, including GRK4(142V), with human essential hypertension in a Japanese population (n=588; hypertensive, n=486 normotensive controls) and determined whether the presence of GRK4 variants predicted the blood pressure (BP) response to angiotensin receptor blockers (ARBs) in patients with essential hypertension. We analyzed 829 patients and compared the response to ARBs between individuals with no GRK4 variants (n=136) and those with variants at one or any of the three loci (n=693). Carriers of hGRK4(142V) had a greater decrease in systolic BP in response to ARBs than non-carrier hypertensive patients. By contrast, those with variants only at GRK4(486V) were less likely to achieve the BP goal in response to an ARB than those with no variants. These studies showed for the first time the association between GRK4(142V) and a larger decrease in BP with ARBs in hypertensive patients.

Differential regulation of renal phospholipase C isoforms by catecholamines.

Dopamine and D1 agonists and NE all increase phosphatidyl inositol-specific phospholipase C (PLC) activity, but whereas dopamine produces a natriuresis, NE has an antinatriuretic effect. To determine if catecholamines differentially regulate the expression of PLC isoforms, we infused fenoldopam, a D1 agonist, or pramipexole, a D1/D2 agonist, intravenously or infused fenoldopam or NE into the renal artery of anesthetized rats. After 3-4 h of infusion, when the expected natriuresis (fenoldopam or pramipexole) or antinatriuresis (NE) occurred, the kidneys were removed for analysis of PLC isoform protein expression activity. Western blot analysis revealed that in renal cortical membranes, fenoldopam and pramipexole increased expression of PLC beta 1 and decreased expression of PLC gamma 1; PLC delta was unchanged. In the cytosol, pramipexole and fenoldopam increased expression of both PLC beta 1 and PLC gamma 1. No effects were noted in the medulla. A preferential D1 antagonist, SKF 83742, which by itself had no effect, blocked the effects of pramipexole, thus confirming the involvement of the D1 receptor. In contrast, NE also increased PLC beta 1 but did not affect PLC gamma 1 protein expression in membranes. The changes in PLC isoform expression were accompanied by similar changes in PLC isoform activity. These studies demonstrate for the first time differential regulation of PLC isoforms by catecholamines.

Role of the D1A dopamine receptor in the pathogenesis of genetic hypertension.

Since dopamine produced by the kidney is an intrarenal regulator of sodium transport, an abnormality of the dopaminergic system may be important in the pathogenesis of hypertension. In the spontaneously hypertensive rat (SHR), in spite of normal renal production of dopamine and receptor density, there is defective transduction of the D1 receptor signal in renal proximal tubules, resulting in decreased inhibition of sodium transport (Na+/H+ exchanger [NHE] and Na+/K+ATPase activity) by dopamine. To determine if impaired D1 receptor regulation of NHE in proximal tubules is related to hypertension, studies were performed in a F2 generation from female Wistar Kyoto (WKY) and male SHR crosses. A D1 agonist, SKF 81297, inhibited (37.6 +/- 4.7%) NHE activity in brush border membranes of normotensive F2s (systolic blood pressure < 140 mm Hg, n = 7) but not in hypertensive F2s (n = 21). Furthermore, a D1 agonist, SKF 38393, when infused into the renal artery, dose dependently increased sodium excretion in normotensive F2s (n = 3) without altering renal blood flow but was inactive in hypertensive F2s (n = 21). Since the major D1 receptor gene expressed in renal proximal tubules is the D1A subtype, we determined the importance of this gene in the control of blood pressure in mice lacking functional D1A receptors. Systolic blood pressure was greater in homozygous (n = 6) and heterozygous (n = 5) mice compared to normal sex matched litter mate controls (n = 12); moreover, the mice lacking one or both D1A alleles developed diastolic hypertension. The cosegregation with hypertension of an impaired D1 receptor regulation of renal sodium transport and the development of elevated systolic and diastolic pressure in mice lacking one or both D1A alleles suggest a causal relationship of the D1A receptor gene with hypertension.

Disruption of the dopamine D3 receptor gene produces renin-dependent hypertension.

Since dopamine receptors are important in the regulation of renal and cardiovascular function, we studied the cardiovascular consequences of the disruption of the D3 receptor, a member of the family of D2-like receptors, expressed in renal proximal tubules and juxtaglomerular cells. Systolic and diastolic blood pressures were higher (approximately 20 mmHg) in heterozygous and homozygous than in wild-type mice. An acute saline load increased urine flow rate and sodium excretion to a similar extent in wild-type and heterozygous mice but the increase was attenuated in homozygous mice. Renal renin activity was much greater in homozygous than in wild-type mice; values for heterozygous mice were intermediate. Blockade of angiotensin II subtype-1 receptors decreased systolic blood pressure for a longer duration in mutant than in wild-type mice. Thus, disruption of the D3 receptor increases renal renin production and produces renal sodium retention and renin-dependent hypertension.

Renal dopamine receptors in health and hypertension.

During the past decade, it has become evident that dopamine plays an important role in the regulation of renal function and blood pressure. Dopamine exerts its actions via a class of cell-surface receptors coupled to G-proteins that belong to the rhodopsin family. Dopamine receptors have been classified into two families based on pharmacologic and molecular cloning studies. In mammals, two D1-like receptors that have been cloned, the D1 and D5 receptors (known as D1A and D1B, respectively, in rodents), are linked to stimulation of adenylyl cyclase. Three D2-like receptors that have been cloned (D2, D3, and D4) are linked to inhibition of adenylyl cyclase and Ca2+ channels and stimulation of K+ channels. All the mammalian dopamine receptors, initially cloned from the brain, have been found to be expressed outside the central nervous system, in such sites as the adrenal gland, blood vessels, carotid body, intestines, heart, parathyroid gland, and the kidney and urinary tract. Dopamine receptor subtypes are differentially expressed along the nephron, where they regulate renal hemodynamics and electrolyte and water transport, as well as renin secretion. The ability of renal proximal tubules to produce dopamine and the presence of receptors in these tubules suggest that dopamine can act in an autocrine or paracrine fashion; this action becomes most evident during extracellular fluid volume expansion. This renal autocrine/paracrine function is lost in essential hypertension and in some animal models of genetic hypertension; disruption of the D1 or D3 receptor produces hypertension in mice. In humans with essential hypertension, renal dopamine production in response to sodium loading is often impaired and may contribute to the hypertension. The molecular basis for the dopaminergic dysfunction in hypertension is not known, but may involve an abnormal post-translational modification of the dopamine receptor.

Attenuated renal response to dopaminergic drugs in spontaneously hypertensive rats.

Activation of renal dopamine-1 receptors decreases sodium transport. However, the spontaneously hypertensive rat retains sodium despite increased renal dopamine concentration. We tested the hypothesis that the abnormal sodium handling in spontaneously hypertensive rats (Okamoto-Aoki strain) is related to a decreased dopaminergic response by studying the effects of the intrarenal infusion of the dopamine-1 agonist SKF-38393 and the dopamine-1 antagonist SCH-23390 in hypertensive and in normotensive Wistar-Kyoto rats. Rats (9-16 weeks old) were studied with renal nerves intact under pentobarbital anesthesia (n = 5-6 in each group). Specificity of dopamine-1 effects of SKF-38393 was verified because its natriuretic effect was blocked in a dose-related manner by the dopamine-1 antagonist SCH-23390 (n = 5). Intrarenal but resulted in a dose-related natriuresis and diuresis in normotensive but not in hypertensive rats. Intrarenal arterial infusion of the dopamine-1 antagonist SCH-23390 alone induced an antinatriuresis, without affecting glomerular filtration rate, in normotensive but not in hypertensive rats. Addition of the dopamine-2 antagonist YM-09151 to the dopamine-1 antagonist infusion did not enhance the effect of the dopamine-1 antagonist. The lack of response to the dopamine-1 agonist or antagonist in hypertensive rats was not due to differences in renal dopamine-1 receptor density (1.3 +/- 0.3 pmol/mg protein for spontaneously hypertensive rats, n = 4; 1 +/- 0.2 for Wistar-Kyoto rats, n = 4) or affinity; distribution determined by autoradiography was also similar. The abnormal renal sodium handling in 9-16-week-old spontaneously hypertensive rats is in part due to decreased response distal to the dopamine-1 receptor.

Laser photocoagulation with biomicroscopic scleral indentation.

The treatment of peripheral retinal tears by laser photocoagulation is an accepted technique. One of its limitations is its difficulty in use near the ora serrata. The inability to treat the anterior border of a rentinal tear may allow the tear to progress to clinical retinal detachment despite treatment of the tear's posterior and lateral borders. The use of a scleral indentation funnel at the time of laser photocoagulation permits the sealing of all margins of the break. This technique increases the number of retinal tears that can be treated by the laser, and it may improve the rate of success of photocoagulation of peripheral retinal tears.

Indentation laser photocoagulation of peripheral retinal neovascularization.

The treatment of peripheral retinal neovascularization by laser photocoagulation is an accepted technique. One of its limitations is the difficulty in photocoagulating retinal neovascularization that has become even slightly elevated from the underlying pigment epithelium. The failure to close the neovascular frond and the production of a vitreous hemorrhage are the complications from the direct photocoagulation of elevated neovascularization. The currently accepted method of treating the feeding retinal arteriole and venule, although successful, requires multiple treatment sessions. The use of a scleral indentation funnel at the time of laser photocoagulation permits the direct photocoagulation of elevated neovascularization in some cases. This technique increases the number of neovascular fronds that are amenable to direct laser photocoagulation, improves the rate of success of closure of the neovascularization by photocoagulation, decreases the necessary number of treatment sessions, and decreases the risks from treatment.

The signal transducer for the dopamine-1 regulated sodium transport in renal cortical brush border membrane vesicles.

We have reported the presence of dopamine-1 (DA-1) and dopamine-2 (DA-2) receptors in renal brush border and basolateral membranes. DA-1 agonists stimulate adenylate cyclase (AC) and phospholipase C (PLC) activity in both membranes. Moreover, the ability of a DA-1 agonist (fenoldopam) to stimulate PLC activity is independent of AC activity. A DA-2 agonist (LY171555) by itself was without effect and did not enhance the ability of the DA-1 agonist to stimulate PLC activity. The DA-1 but not DA-2 agonists inhibit Na+/H+ exchange activity in brush border membrane vesicles (BBMV) and Na+/K(+)-ATPase activity in basolateral membranes. However, cAMP inhibits, while protein kinase C (presumably via PLC activity) stimulates, Na+/H+ exchange activity. We therefore determined the effect of DA-1 agonists on Na+/H+ exchange activity when PLC or AC activity was blocked using neomycin or dideoxyadenosine, respectively. The drugs were incubated with minced renal cortex prior to preparation of BBMV by differential centrifugation and MnCl2 precipitation. Enrichment of BBMV was not affected by drug treatment. The Na+/H+ exchange activity was assessed by measuring amiloride (1 mmol/L) sensitive 22Na+ uptake in BBMV (pHi = 5.5, pHo = 7.5, Nai+ = O, Nao+ = 1 mmol/L). Neomycin inhibited DA and DA-1-stimulated PLC activity in BBMV in a concentration dependent manner (10(-6) to 10(-4) mol/L). Neomycin (10(-4) mol/L) completely blocked the ability of DA and DA-1 agonist to stimulate PLC activity but had no consistent effect on DA-1 inhibited Na+/H+ exchange activity. Dideoxyadenosine inhibited DA and DA-1 simulated AC activity without affecting DA-1 stimulated PLC activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Dopamine receptor signaling defects in spontaneous hypertension.

Dopamine produced by renal proximal tubules acts as an intrarenal natriuretic factor by direct tubular action; this paracrine effect is influenced by the state of sodium balance. Up to 60% of sodium excretion with volume (2%-10%) expansion may be mediated by D1-like receptors. The renal paracrine effect of dopamine is impaired in genetic hypertension; this is due to defects in renal dopamine production or transduction of the dopamine signal. The Dahl salt sensitive rat and the spontaneously hypertensive rat (SHR), which have normal renal dopamine production and expression of dopamine receptors, have a defect in the coupling of a D1-like receptor to G-protein/effector enzyme complex. A consequence of the defective D1-like receptor/effector enzyme coupling in SHR is a decreased ability of D1 agonists to inhibit Na+/H+ exchange and Na+/K+-ATPase activity. The defect is 1) genetic, since it precedes the onset of and cosegregates with the hypertension; 2) receptor specific, since it is not shared by other humoral agents; and 3) confined to the renal proximal tubule. Two of the cloned dopamine receptors in mammals are D1-like (D1A and D1B). The D1A receptor gene is expressed to a greater extent in renal proximal tubules than the D1B receptor gene. The D1-like receptor is important in the pathogenesis of hypertension. Chronic blockade of dopamine receptors accelerates the development of hypertension in normotensive and hypertensive rats. Moreover, disruption of the D1A receptor gene in mice increases systolic blood pressure and results in diastolic hypertension. The abnormal D1-like receptor in SHR may be the D1A receptor; its uncoupling from the G-protein/effector enzyme complex in renal proximal tubules of SHR may be due to mistargeting. The mechanism for this "mistargeting" of the D1A receptor is not due to a mutation in the primary sequence and remains to be determined.

A multicenter comparison of the safety and efficacy of isradipine and enalapril in the treatment of hypertension.

This multicenter trial compared the efficacy and safety of isradipine and enalapril in 160 patients with essential hypertension. Patients received isradipine or enalapril for 10 weeks after a placebo wash-out period of three to five weeks. Dosage was titrated for six weeks on the basis of blood pressure (BP) response and was then maintained for the remainder of the study. Isradipine reduced systolic and diastolic BP by 12 and 9 mm Hg, respectively, and enalapril by 10 and 7 mm Hg, respectively (between-treatment difference P less than .05 for diastolic BP). Overall, isradipine resulted in a higher responder rate, particularly among patients who had higher entry BPs. Fifteen enalapril-treated patients and four isradipine-treated patients discontinued treatment (four taking enalapril and none taking isradipine withdrew because of lack of efficacy). The most frequently reported adverse reactions were headache, dizziness, and edema in the isradipine group, and cough, headache, and chest pain in the enalapril group. Both drugs produced significant reductions in BP, but, in this study isradipine was more effective. The drugs were similarly well tolerated.

Dopamine D1 receptor regulation of phospholipase C.

Dopamine is an endogenous catecholamine which exerts its actions by occupancy of specific receptors. Dopamine receptors are classified into two main groups: the two cloned D1-like receptors (D1A and D1B in rats; D1B is also known as D5 in humans) are linked to stimulation of adenylyl cyclase, while the three cloned D2-like receptors (D2 or D2A, D3 or D2B, D4 or D2C) are linked to inhibition of adenylyl cyclase. All these dopamine receptors originally cloned from the brain are expressed in tissues outside the central nervous system including the kidney. Dopamine regulates many cellular activities, including transmembrane ion transport. Activation of D1-like receptor decreases sodium transport by cAMP dependent and cAMP independent mechanisms. Dopamine, via D1-like receptors, may inhibit Na+/H+ exchange activity in renal brush border membranes by a cAMP independent/Gs alpha-linked mechanism. Another cAMP independent pathway of sodium transport inhibition is mediated by phospholipase C, which has several isoforms (PLC beta, PLC gamma, and PLC delta with several members in each). Catecholamines stimulate expression and activity of phospholipase C isoforms in a concentration, time, and receptor-dependent as well as regional and subcellular compartmental-specific manner. In renal cortical membranes, intrarenal administration of norepinephrine for 3-4 h increases PLC beta expression and activity but has no effect on PLC gamma activity. In contrast, intrarenal administration of a D1 agonist for 3-4 h increases PLC beta 1 but decreases PLC gamma expression and activity.(ABSTRACT TRUNCATED AT 250 WORDS)

A multicenter comparison of adverse reaction profiles of isradipine and enalapril at equipotent doses in patients with essential hypertension.

A multicenter, randomized, double-blind trial compared the safety and efficacy of the dihydropyridine isradipine with the angiotensin-converting enzyme (ACE) inhibitor enalapril given twice daily for mild hypertension. 160 patients received either isradipine (starting at 1.25 mg twice daily) or enalapril (starting at 2.5 mg twice daily) for 10 weeks. The dosage was increased if the average sitting diastolic blood pressure was > 90 mm Hg. Significantly greater mean reductions in systolic blood pressure were seen after 2, 6, and 8 weeks of isradipine. However, by the end of the trial, 83% of patients receiving isradipine and 78% receiving enalapril showed a decrease of at least 5 mm Hg in sitting diastolic blood pressure to a level below 96 mm Hg. Possible or probable drug-related adverse effects were reported in 36% of patients showing a good antihypertensive response to isradipine, and in 30% of those who responded to enalapril. There was a trend for a lower frequency of adverse effects in isradipine non-responders (25%) and a higher frequency in enalapril non-responders (43%). Pruritus, dizziness, edema, and fatigue were reported more often with isradipine, and cough and changed bowel habits were more common with enalapril. The relationship between the pattern of adverse effects and the extent of blood pressure reduction may be dependent on the mechanism of action of a drug. In responders, isradipine and enalapril showed differing patterns, but a similar overall incidence of adverse effects.

Dopamine receptors in hypertension.

There is increased awareness of the role of dopamine in cardiovascular function, renal function and systemic blood pressure regulation. Growing evidence indicates that each of the five dopamine receptor subtypes participates in the regulation of blood pressure by mechanisms distinct for that particular subtype. Some dopamine receptors regulate blood pressure by influencing the central and peripheral nervous system, while others influence renal function and release of renin, aldosterone and vasopressin. This review summarizes the physiology and pathophysiology of the peripheral dopaminergic system and our current understanding of the role of individual dopamine receptors in the pathophysiology of human essential hypertension.

Renal hemodynamics and natriuresis induced by the dopamine-1 agonist, SKF 82526.

The intrarenal infusion of dopamine (DA) during alpha- and beta-adrenergic blockade has been reported to increase renal blood flow (RBF) and sodium excretion by occupation of DA-1 receptors. In addition, DA may potentially influence renal function by occupation of DA-2 receptor subtypes. This study was designed to examine the hemodynamic and/or tubular mechanisms of the natriuretic effect of DA-1 in dogs anesthetized with pentobarbital. The intrarenal infusion of the DA-1 agonist, SKF 82526 (10(-9), 10(-8), 10(-7) M), resulted in dose related increases in RBF and absolute and fractional sodium excretion. These changes were not associated with alterations in urinary prostaglandin E2, F2 alpha, or kallikrein excretion. To determine the role of RBF in the natriuresis due to SKF 82526 infusion (10(-7) M), the renal artery was constricted to return RBF to control levels during continued SKF 82526 infusion. Although absolute and fractional sodium excretion decreased during this maneuver, they remained higher than control. These studies support both a hemodynamic and a tubular mechanism for the natriuretic effect of the DA-1 agonist, SKF 82526. These effects do not appear to be mediated by the renal prostaglandin or kallikrein systems.

[Comparative study of the repeated nucleotide sequences in DNA from differentiated tissues and tumors]. / Sravnitel'noe issledovanie povtoriaiushchikhsia nukleotidnykh posledovatel'nosv v DNK differentsirovannykh tkanei i pri malignizatsii

DNA renaturation kinetics was measured for the genomes of normal (spleen) and malignant (plasmacytoma) mouse tissues and for DNA from liver, sperm and developing embryos of the loach. It has been shown that the measuring of DNA renaturation kinetics makes it possible to reveal differences in the content of certain fractions of the repetitions in the genomes of different species. Moreover, differences in the distribution of the repetitions between hetero- and euchromatine can be identified. Loach embryo DNA (blastula stage) was shown to contain larger amount of the fraction renaturing at Cot less than 10(-2) as compared to liver and sperm DNAs (by 5%). An enrichment with respect to the intermediate repetitions (10(-2) less than Cot less than 10(2)) was found in the mouse plasmacytoma DNA as compared to the spleen DNA. The nature of these distinctions is discussed.

[Ribosomal genes of the loach Misgurnus fossilis L. Isolation and restriction analysis]. / Ribosomnye geny v'iuna Misgurnus fossilis L. Vydelenie i restriktsionnyi analiz.

The ribosomal DNA of the teleost fish--loach has been isolated from sperm DNA by CsCl density gradient centrifugation. The rDNA sediments on density gradients by two heavy satellites beta = 1.715 and greater than 1.720. The DNA of the first satellite (1.715) was separated and treated by restrictases EcoRI and BamHI. It was shown that there are two EcoRI-sites in rDNA of loach, locating in 18S and 28S rRNA coding sequences. From tandem of repeating ribosomal genes EcoRI cuts out the fragment with homogeneous length-3 megadaltons (constant fragment) and heterogeneous population of fragments 11-13 megadaltons (major) and 7-8 megadaltons (minor fraction). The constant fragment contains mostly 28S coding sequence, and the heterogeneous fragment--18S coding sequence. The data indicate that the ribosomal genes of the loach as well as other higher eucaryotes were organized in genome as tandem of repeating units with heterogeneous length (10-16 megadaltons, 14.5-24 kb) due to heterogeneity of the length of nontranscribed spacer.

[Regulation of NHE3 by D1 dopamine receptor during development of spontaneously hypertensive rats].

OBJECTIVE: To determine if spontaneous hypertension is secondary to defective interaction among dopamine receptor, G protein, and Na(+)/H(+) exchanger 3 (NHE3). METHODS: The inhibitory effect of a D(1) dopamine agonist upon NHE3 activity and its impact upon G(s)alpha/NHE3 binding in renal brush border membrane (BBM) of spontaneously hypertensive rats (SHRs) 2 - 3 weeks before and 12 weeks after the establishment of hypertension were examined. In order to avoid the confounding influence of second messenger on D(1) receptor/NHE3 interaction, study was made in BBM devoid of cytoplasmic component. RESULTS: NHE3 activity increased with age in Wister-Kyoto (WKY) rats but not in SHRS. D1 receptor expression did change with age in both WKY rats and SHRs. The inhibitory effect of a D(1)-like agonist on NHE3 activity increased with age in WKY rats but not in SHRs. In WKY rats, another D(1)-like agonist, fedoldopam, increased G(s)alpha/NHE3 binding to the same extent in 2 week old and adult rats, but decreased the amount of G(s)(alpha)bound to NHE3 in 2 week old SHRs. CONCLUSION: The decrease of inhibitory effect of D(1)-like agonist upon NHE3 activity in SHRs precedes the development of hypertension. Spontaneous hypertension may be caused, in part, by a decreased interaction between G(s)alpha and NHE3 in BBM secondary to D(1)-like receptor function.

[Effects and side effects of the drug "Success"]. / Wirkungen und Nebenwirkungen der Droge "Erfolg".

To raise the rate of success to 100% is certainly a goal worth striving for. However, the closer one approaches this ultimate success, the more one is confronted with unexpected difficulties, such as difficulties in recognizing and proving, extremely high success rates as well as ethical problems. Furthermore, in the range of a high success rate all attempts for further amelioration necessarily lead to deterioration of this success rate; this is illustrated by an example from ophthalmology. Actually, coping with success is a great challenge, and the teaching requires not only great skills but also a solid philosophical background. Teachers must meet high demands. This applies also to the general public and the authorities acting in its name who have to appoint gifted teachers and have to support their mission.