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H R Jacobson

Publications and source records attributed to H R Jacobson.

At least 19 recordsLinked to original sources
PubMed1996

Cloning and expression of the rabbit prostaglandin EP4 receptor.

Prostaglandin E2 (PGE2) is an important regulator of systemic hemodynamics and epithelial ion transport. To further investigate the mechanism of PGE2 action, a clone encoding a PGE2 receptor was isolated from a rabbit kidney cortex cDNA library. Expression of the full-length cDNA in COS-1 cells yielded a ligand-binding profile typical for a butaprost-insensitive Gs-coupled E-prostanoid (EP) receptor. Misoprostol-free acid, a receptor-selective PGE analogue, produced concentration-dependent increases in adenosine 3',5'-cyclic monophosphate production. The data are consistent with the receptor being an EP4 subtype. Ribonuclease protection assays demonstrated that this receptor gene is highly expressed in intestine, uterus, and thymus, with lower but significant expression in kidney, whole adrenal, lung, spleen, and stomach. In situ hybridization in kidney revealed intense hybridization to glomeruli and urothelium of the renal pelvis. This prostanoid receptor was also highly expressed in the duodenal epithelium and adrenal cortex. The tissue distribution suggests a functional role for this receptor in mediating glomerular effects of PGE2 and effects on aldosterone secretion, intestinal transport, and immune function.

Amino Acid Sequence↗
PubMed1996

Differential localization of prostaglandin E receptor subtypes in human kidney.

Four prostaglandin E2 (PGE2) receptors designated EP1, EP2, EP3, and EP4 have been pharmacologically identified, cloned, and sequenced. The present studies determined the intrarenal distribution of these EP-receptor subtypes in human kidney using in situ hybridization with riboprobes for the human EP receptors. mRNA for the phosphatidylinositol hydrolysis-coupled EP receptor was highly expressed in cortical, outer medullary, and inner medullary collecting duct. RNA for the Gi-coupled EP3 receptor was primarily expressed in the cortical and outer medullary collecting duct, as well as in the medullary thick ascending limb; however, it was absent from the inner medullary collecting duct. Expression of mRNA for EP1 and EP3 in connecting segment could not be excluded. There was no expression of the GS-coupled EP2 receptor mRNA detected in human kidney by in situ hybridization; however, mRNA for the GS-coupled EP4 receptor was highly expressed in the glomerulus. These studies demonstrate distinct regions of intrarenal expression for the different EP receptors and suggest that each receptor subtype may modulate different aspects of renal function in humans.

Autoradiography↗
PubMed1996

Functional and molecular aspects of renal prostaglandin receptors.

The diverse intrarenal effects of the prostaglandins (PG) are mediated by distinct guanine nucleotide regulatory protein (G-protein)-coupled receptors. The cDNA for these receptors have been cloned, their signal transduction mechanisms determined, and their intrarenal distribution mapped. PGE2, the major intrarenal prostaglandin, interacts with at least three distinct E-prostanoid (EP) receptors that are highly expressed in specific regions of the kidney. Each EP receptor not only selectively binds PGE2, but also preferentially couples to different signal transduction pathways, including: stimulation of cAMP generation, via Gq (EP2 and EP4 receptors); inhibition of cAMP generation, via Gi (EP3 receptors); and activation of phosphatidylinositol hydrolysis (EP1 receptor), via one of the Gq family members. Activation of each these EP receptors is responsible for a distinct renal effect of PGE2, including its well-described renal hemodynamic and transport effects along the nephron. Other intrarenal prostanoid receptors include the PGF2 alpha receptor (FP), the thromboxane A2 receptor (TP) and the prostacyclin receptor (IP). Knowledge about localization of these receptors and their affinities for receptor-selective agonists and antagonists should aid in the understanding of renal disease and the development of therapeutic strategies for the use of these prostaglandin analogs in select renal diseases.

Animals↗
PubMed1995

Functional and molecular aspects of prostaglandin E receptors in the cortical collecting duct.

Endogenous prostaglandin (PG) E2 production potently modulates salt and water transport in the kidney. Multiple direct effects of PGE2 on epithelial water and sodium transport have been demonstrated in the rabbit cortical collecting duct (CCD). Both functional and molecular studies now suggest that these disparate effects of PGE2 on CCD function are mediated by different EP receptors. When added in the presence of vasopressin, PGE2 inhibits cyclic AMP generation and water absorption. These effects are mediated via an inhibitory G-protein (Gi). In situ hybridization demonstrates high levels of expression of the Gi-coupled EP3 receptor in the rabbit collecting duct. However, by itself, PGE2 also stimulates cyclic AMP generation and water permeability. These effects appear to be mediated via a distinct EP receptor (possibly an EP4 receptor). PGE2 also increases intracellular Ca2+ in the CCD and inhibits Na+ absorption via a Ca(2+)-dependent mechanism. The EP1 receptor is postulated to be responsible for this action of PGE2. We suggest receptor-selective prostaglandin analogs may be used to selectively modulate sodium and water transport in the kidney.

Animals↗
PubMed1995

5,6-EET inhibits ion transport in collecting duct by stimulating endogenous prostaglandin synthesis.

We examined the mechanism by which the cytochrome P-450 metabolite of arachidonate, 5,6-epoxyeicosatrienoic acid (5,6-EET), modulates electrogenic transport in the rabbit cortical collecting duct (CCD). 5,6-EET depolarized transepithelial voltage (VT) in a concentration-dependent manner with a maximal effect at 1 microM. None of the other EET regioisomers (8,9-, 11,12-, or 14,15-EET; all at 1 microM) affected VT, This action was also stereoselective, with 5(S),6(R)-EET producing a 2.5-fold greater effect on VT than 5(R),6(S)-EET (1 microM each). Like basolateral prostaglandin E2 (PGE2), both luminal and basolateral 5,6-EET increased cytosolic Ca2+ concentration ([Ca2+]i) in the rabbit CCD. Pretreatment with cyclooxygenase inhibitors (10 microM ibuprofen or 5 microM indomethacin) completely blocked both the [Ca2+]i increase and the change in VT. Neither 5,6-epoxy-PGE1 nor 5-hydroxy-PGI1, cyclooxygenase metabolites of 5,6-EET, affected VT. However, when added to primary cultures of rabbit CCDs, 5,6-EET stimulated endogenous PGE2 synthesis. We propose that 5,6-EET stimulates endogenous prostaglandin synthesis, which inhibits electrogenic ion transport in the CCD.

8,11,14-Eicosatrienoic Acid↗
PubMed1995

Luminal prostaglandin E receptors regulate salt and water transport in rabbit cortical collecting duct.

Prostaglandin E2 (PGE2) is the major renal cyclooxygenase metabolite of arachidonic acid. Urinary excretion of PGE2 is increased by dietary salt restriction, as well in cirrhosis and congestive heart failure. To determine whether urinary PGE2 affects transport along the nephron, the actions of luminal PGE2 were studied in the isolated perfused rabbit cortical collecting duct (CCD). Luminal PGE2 transiently hyperpolarized transepithelial voltage (Vt) in a dose-dependent manner (half-maximal effect approximately 10(-8) M) in contrast to a sustained depolarization of Vt produced by basolateral PGE2. Luminal PGE2 (0.1 microM) also significantly stimulated osmotic water permeability in the CCD. In CCDs cultured on semipermeable supports, apical PGE2 stimulated adenosine 3',5'-cyclic monophosphate (cAMP) production, suggesting the effects of luminal PGE2 are mediated by adenylyl cyclase-stimulating EP2 or EP4 receptors. Sulprostone, a PGE2 analogue selective for EP1 and EP3 receptors, affected Vt only when applied from the basolateral but not the luminal surface. Luminal application of the EP2 receptor agonist butaprost was also without effect. These results suggest that luminal PGE2 affects Vt via a butaprost-insensitive EP4 receptor. The Vt effect of luminal PGE2 was not blocked by pertussis toxin, also arguing against an EP3-mediated Gi-coupled effect. Finally, 1 microM luminal PGE2 only slightly increased CCD intracellular calcium concentration ([Ca2+]i), in contrast to the marked increase in [Ca2+]i produced by basolateral PGE2 (0.1 microM).(ABSTRACT TRUNCATED AT 250 WORDS)

Adenylate Cyclase Toxin↗
PubMed1994

Experimental and/or genetically controlled alterations of the renal microsomal cytochrome P450 epoxygenase induce hypertension in rats fed a high salt diet.

Excess dietary salt induces a cytochrome P450 arachidonic acid epoxygenase isoform in rat kidneys (Capdevila, J. H., S. Wei, J. Yang, A. Karara, H. R. Jacobson, J. R. Falck, F. P. Guengerich, and R. N. Dubois. 1992. J. Biol. Chem. 267:21720-21726). Treatment of rats on a high salt diet with the epoxygenase inhibitor, clotrimazole, produces significant increases in mean arterial blood pressure (122 +/- 2 and 145 +/- 4 mmHg for salt and salt- and clotrimazole-treated rats, respectively). The salt- and clotrimazole-dependent hypertension is accompanied by reductions in the urinary excretion of epoxygenase metabolites and by a selective inhibition of the renal microsomal epoxygenase reaction. The prohypertensive effects of clotrimazole are readily reversed when either the salt or clotrimazole treatment is discontinued. The indication that a salt-inducible renal epoxygenase protects against hypertension, are supported by studies with the Dahl rat model of genetic salt-sensitive hypertension. Dahl resistant animals responded to excess dietary salt by inducing the activity of their kidney microsomal epoxygenase(s) (0.102 +/- 0.01 and 0.240 +/- 0.04 nmol of products formed/min per mg of microsomal protein for control and salt-treated rats, respectively). Despite severe hypertension during excess dietary salt intake (200 +/- 20 mmHg), Dahl salt-sensitive rats demonstrated no increase in renal epoxygenase activity. These studies indicate that acquired or inherited abnormalities in renal epoxygenase activities and/or regulation can be related to salt-sensitive hypertension in rodents. Studies on the human renal epoxygenase and its relationship to salt hypertension may prove useful.

Animals↗
PubMed1994

Cyclooxygenase-2 is associated with the macula densa of rat kidney and increases with salt restriction.

The kidney is a rich source of prostaglandins. These eicosanoids, formed by cyclooxygenase-dependent metabolism of arachidonic acid, are important physiologic mediators of renal glomerular hemodynamics and tubular sodium and water reabsorption. Two separate isoforms of cyclooxygenase (COX) have now been identified: constitutive COX-1, encoded by a 2.8-kb mRNA, and mitogen-activated COX-2, encoded by a 4.0-4.5-kb mRNA. COX-2 expression increases during development and inflammation, but, except for brain, constitutive expression is low. It has been generally accepted that physiologic renal production of prostaglandins is mediated by COX-1. However, in the absence of inflammation, low levels of COX-2 mRNA are also detectable in the kidney. To examine the role of COX-2 in the kidney and determine its intrarenal localization, we used a 1.3-kb cDNA probe specific for the 3' untranslated region of rat COX-2 and COX-2-specific antiserum. The COX-2-specific cDNA probe hybridized with a 4.4-kb transcript in total RNA from adult rat kidney. Immunoblots of microsomes isolated from kidney cortex and papilla indicated immunoreactive COX-2 in both locations. In situ hybridization and immunohistochemistry indicated that renal cortical COX-2 expression was localized to the macula densa of the juxtaglomerular apparatus and to adjacent epithelial cells of the cortical thick ascending limb of Henle. In addition, COX-2 immunoreactivity was detected in interstitial cells in the papilla. No COX-2 message or immunoreactive protein was detected in arterioles, glomeruli, or cortical or medullary collecting ducts. When animals were chronically sodium restricted, the level of COX-2 in the region of the macula densa increased threefold (from 0.86 +/- 0.08 to 2.52 +/- 0.43/mm2) and the total area of the COX-2 immunoreactive cells in cortex increased from 34 microns2/mm2 of cortex to 226 microns2/mm2 of cortex. The intrarenal distribution of COX-2 and its increased expression in response to sodium restriction suggest that in addition to its proposed role in inflammatory and growth responses, this enzyme may play an important role in the regulation of salt, volume, and blood pressure homeostasis.

Animals↗
PubMed1993

Molecular cloning, expression, and enzymatic characterization of the rat kidney cytochrome P-450 arachidonic acid epoxygenase.

A cDNA containing an open reading frame coding for the rat kidney cytochrome P-450 arachidonic acid epoxygenase was isolated from a male rat kidney cDNA library. Sequence analysis showed that with the exception of 11 nucleotides, this cDNA is identical with the published sequence for rat liver cytochrome 2C23 and encodes a polypeptide of 494 amino acids. Nucleic acid blot hybridization indicated that the levels of expression of the corresponding mRNA are high in rat kidney and liver and are undetectable in brain and heart. The cDNA coding region was cloned into a pCMV2 vector and expressed in COS-1 cells. The recombinant microsomal protein catalyzed the NADPH-dependent metabolism of arachidonic acid to a mixture of 5,6-, 8,9-, 11,12-, and 14,15-epoxyeicosatrienoic acids as the only oxygenation products. The enantiofacial selectivity of the recombinant protein was nearly identical with that reported for the kidney microsomal enzyme and generated 8(R),9(S)-, 11(R),12(S)-, and 14(S),15(R) with optical purities of 95, 85, and 75%, respectively. On the basis of mRNA abundance and the close similarities between the regio- and stereochemical selectivity of the recombinant and kidney microsomal proteins, we concluded that cytochrome P-450 2C23 is the predominant enzyme isoform responsible for arachidonic acid epoxidation in the rat kidney.

Amino Acid Sequence↗
PubMed1993

In situ hybridization and localization of mRNA for the rabbit prostaglandin EP3 receptor.

The physiological effects of PGE2 appear to be mediated by at least three different "E-prostanoid" receptors designated EP1,EP2, and EP3. These receptors are differentially activated by structural PGE analogs (such as misoprostol) and each couples to a different signal transduction mechanism. Studies demonstrating that inhibition of water absorption in the collecting duct is mediated by a Gi coupled mechanism, suggests that an EP3 receptor is involved the renal effects of PGE2. We used in situ hybridization to determine the tissue distribution of the rabbit EP3 receptor. [alpha-35S] UTP labeled antisense RNA, comprising transmembrane domains IV through VII, was hybridized to tissue sections. Specific labeling of kidney, stomach and adrenal was observed. In the kidney, medullary thick ascending limb and cortical and medullary collecting ducts were intensely labeled, while no labeling of glomeruli, proximal tubules, or cortical thick ascending limbs was observed. The adrenal gland labeled exclusively in the medulla. In the stomach the gastric epithelial crypts were the predominant site of hybridization, without evidence of labeling of the smooth muscle. These results suggest an important role for the EP3 receptor in mediating PGE2 effects in these tissues.

Adrenal Glands↗
PubMed1993

Ischemic nephropathy.

Data suggest that ischemic renal disease secondary to atherosclerotic renal artery stenosis is a prevalent health problem. Atherosclerotic renal artery stenosis is a rapidly progressive process that can result in end-stage renal disease. Renal arteriography is the current diagnostic method of choice for the demonstration of renal artery stenosis. Captopril renography, nuclear magnetic resonance angiography, and duplex scanning are promising screening tests for this disorder. Therapeutic options include medical management, percutaneous angioplasty, and surgical revascularization.

Humans↗
PubMed1993

Evidence for basolateral membrane Ca2+/H+ exchange in outer medullary collecting duct.

The relationship between Ca2+ and intracellular pH (pHi) was studied in the rabbit collecting duct from the inner stripe of the outer medulla (OMCDi). When bath Ca2+ was lowered [1 mM Ca2+ plus 2 mM ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA)] intracellular Ca2+ concentration ([Ca2+]i) decreased by 38.3 +/- 6.2% from 265 +/- 25 to 165 +/- 25 nm (n = 4). Lowering bath Ca2+ produced a biphasic response in pHi, transient acidification (from 6.93 +/- 0.06 to 6.80 +/- 0.06) followed by a return of pHi to levels slightly higher than control (pHi = 6.97 +/- 0.06). The acidification was not blocked by bath amiloride or 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS) or lumen N-ethylmaleimide (NEM). However, bath amiloride significantly reduced the initial rate of pHi recovery after acidification (0.70 pH U/min in control vs. 0.39 pH U/min with amiloride). Lanthanum, a Ca2+ pump inhibitor, completely inhibited the acidification. Moreover, lowering bath temperature to 20 degrees C also inhibited the acidification. Acidification was blocked when the bath pH was raised to 8.0, whereas lowering bath Ca2+ markedly acidified cells when bath pH was lowered to 6.0 (delta pHi = 0.28 +/- 0.01). We also measured the transepithelial (Vt) and basolateral (Vbl) membrane voltages. Lowering bath Ca2+ depolarized Vt and Vbl by 12.7 +/- 4.9 and 6.0 +/- 2.0 mV, respectively. In summary, 1) lowering bath Ca2+ caused a biphasic response in pHi of OMCDi cells, and 2) the acidification phase is due to H+ influx associated with the Ca2+ pump.

Animals↗
PubMed1993

Evidence that separate PGE2 receptors modulate water and sodium transport in rabbit cortical collecting duct.

Prostaglandin E2 (PGE2) modulates both water and sodium transport in the rabbit cortical collecting duct (CCD). To determine whether these effects are mediated by separate PGE2 receptors, we compared the effects of PGE2 and its analogue sulprostone in the isolated perfused rabbit CCD. PGE2 increased basal water permeability (hydraulic conductivity), whereas sulprostone did not. PGE2 and sulprostone were equipotent inhibitors of water absorption when it was prestimulated by vasopressin. Pertussis toxin completely reversed the inhibitory effect of sulprostone but only partially reversed the inhibitory effect of PGE2. In contrast, a protein kinase C (PKC) inhibitor, staurosporine, partially reversed the inhibitory effect of PGE2 but had no effect on sulprostone. PGE2 also raised intracellular calcium ([Ca2+]i). This effect is coupled to its capacity to inhibit Na+ absorption. Sulprostone was 10-fold less potent than PGE2 both in raising [Ca2+]i or inhibiting sodium transport. The results suggest sulprostone selectively interacts with a PGE2 receptor coupled to pertussis toxin-sensitive inhibition of water permeability. Sulprostone less potently activates a PGE2 receptor coupled to [Ca2+]i, PKC activation, and sodium transport and completely fails to interact with the PGE2 receptor that stimulates water permeability in the collecting duct. These results suggest distinct PGE2 receptors modulate sodium and water transport in the CCD.

Alkaloids↗
PubMed1993

Induction of renal arachidonate cytochrome P-450 epoxygenase after uninephrectomy: counterregulation of hyperfiltration.

After unilateral nephrectomy (UNx) in the rat, cytochrome P-450 (cP-450)-linked arachidonate enzymatic activity was markedly and specifically induced in microsomal fractions from the remaining kidney. The enzymatic activity reached 200% at 1 wk and 285% at 2 wk post-UNx as compared with non-UNx controls. Mean baseline values for GFR and RPF rate in the remaining kidney 2 wk after UNx were 1.56 +/- 0.10 and 6.47 +/- 0.35 mL/min, respectively. In these rats, the administration of ketoconazole, a cP-450 inhibitor, led to 75% inhibition of renal cP-450 arachidonate metabolism and was associated with acute augmentations in both GFR and RPF to 1.82 +/- 0.18 (P < 0.05 versus baseline) and 7.54 +/- 0.37 mL/min (P < 0.05 versus baseline), respectively. Because vasoconstrictor arachidonate epoxygenase products are endogenously generated in the rat kidney, these findings suggest that the stimulation of renal cP-450-mediated oxygenation of arachidonic acid may subserve an important counterregulatory function in mitigating the renal hyperperfusion and hyperfiltration that follow reductions in renal mass.

Alkaline Phosphatase↗
PubMed1992

Cytochrome P-450 arachidonic acid epoxygenase. Regulatory control of the renal epoxygenase by dietary salt loading.

The rat kidney microsomal epoxygenase catalyzed the asymmetric epoxidation of arachidonic acid to generate as major products: 8(R),9(S)-, 11(R),12(S)- and 14(S),15(R)-epoxyeicosatrienoic acids with optical purities of 97, 88, and 70%, respectively. Inhibition studies utilizing a panel of polyclonal antibodies to several rat liver cytochrome P-450 isoforms, indicated that the renal epoxygenase(s) belongs to the cytochrome P-450 2C gene family. Dietary salt, administered either as a 2-2.5% (w/v) solution in the drinking water or as a modified solid diet containing 8% NaCl (w/w), resulted in marked and selective increases in the renal microsomal epoxygenase activity (416 and 260% of controls, for the liquid and solid forms of NaCl, respectively) with no significant changes in the microsomal omega/omega-1 oxygenase or in the hepatic arachidonic acid monooxygenase reaction. Immunoblotting studies demonstrated that dietary salt induced marked increases in the concentration of a cytochrome P-450 isoform(s) recognized by polyclonal antibodies raised against human liver cytochrome P-450 2C10 or rat liver cytochrome P-450 2C11. Comparisons of the stereochemical selectivity of the induced and non-induced microsomal epoxygenase(s) with that of purified rat liver cytochrome P-450 2C11 suggest that the salt-induced protein(s) is catalytically and structurally different from liver cytochrome P-450 2C11. The in vivo significance of dietary salt in regulating the activities of the kidney endogenous arachidonic acid epoxygenase was established by the demonstration of a salt-induced 10-20-fold increase in the urinary output of epoxygenase metabolites. These results, in conjunction with published evidence demonstrating the potent biological activities of its metabolites, suggest a role for the epoxygenase in the renal response to dietary salt.

8,11,14-Eicosatrienoic Acid↗
PubMed1992

Mesangial deposition of type I collagen in human glomerulosclerosis.

The presence of type I collagen in both diffuse and nodular diabetic glomerular lesions has been examined using immunohistochemical and electron microscopic techniques. At the ultrastructural level, banded collagen fibrils were observed in the mesangium in all cases of nodular (Kimmelstiel-Wilson) sclerosis and in 60% of the diffuse sclerotic lesions. Antibodies against type I collagen were localized in the fibrotic interstitium and the mesangium in all cases examined. Staining with type I collagen antibodies occurred in glomeruli with intact Bowman's capsules, and was predominantly localized to areas immediately adjacent to mesangial cells. In cases of focal sclerosis of nondiabetic origin, banded collagen fibrils and staining with anti-type I collagen antibody were observed in all cases in which the segmental lesion was presented in the specimen. The pattern of antibody localization in both the diabetic lesions and focal sclerosis differed from that obtained using anti-type IV (basement membrane) collagen antibodies. These results demonstrate that type I collagen is among the extracellular matrix components that comprise the sclerotic glomerular lesions of both diabetic and nondiabetic origin. Furthermore, the spatial localization of this collagen type suggests mesangial cell origin.

Collagen↗
PubMed1992

PGE2 regulates cAMP production in cultured rabbit CCD cells: evidence for dual inhibitory mechanisms.

In cultured cortical collecting duct (CCD) cells, exogenous prostaglandin E2 (PGE2) inhibited arginine vasopressin (AVP)-stimulated adenosine 3',5'-cyclic monophosphate (cAMP) production in a concentration-dependent manner. Although pertussis toxin (PT, 500 ng/ml) alone did not reverse the PGE2-dependent inhibition, PT and staurosporine, a protein kinase C inhibitor, together partially reversed the effect of exogenous PGE2. In contrast, PT completely reversed the inhibition of AVP-dependent cAMP production by sulprostone. These data suggest that exogenous PGE2 can inhibit AVP-stimulated cAMP production and that the inhibitory effects of PGE2 are mediated by staurosporine- and PT-sensitive component(s). Short-term (15-240 min) incubation with phorbol 12-myristate 13-acetate (PMA, 10(-7) M) inhibited PGE2-stimulated cAMP production. Long-term (20 h) incubation with PMA augmented PGE2-stimulated cAMP production. These data provide evidence for the maintenance of a PT-sensitive PGE2-dependent inhibitory pathway of cAMP production in cultured CCD cells. In addition, data are presented that support an inhibitory role for protein kinase C in the effects of PGE2 on the metabolism of cAMP in these cells.

Alkaloids↗