Diagnostic performance of MR imaging of three major salivary glands for Sjögren's syndrome.

OBJECTIVE: We analyzed the diagnostic performance of the MR imaging findings of the parotid, submandibular, and sublingual glands to discriminate between patients with and without Sjögren's syndrome. METHODS: We retrospectively analyzed the correlation between the MR imaging and histopathological findings obtained from 69 patients with clinically suspected Sjögren's syndrome. We evaluated the heterogeneous signal intensity distribution on T1- and T2-weighted images, the multiple high-signal-intensity spots on MR sialograms, and the volume of the parotid, submandibular, and sublingual salivary glands. RESULTS: The multiple high-signal-intensity spots in the parotid gland showed the highest sensitivity and diagnostic accuracy (82% and 83%, respectively). In addition, the multiple high-signal-intensity spots and the heterogeneous signal intensity distribution in the submandibular gland showed high specificity (100% and 88%, respectively). The volume of the submandibular gland, but not that of the parotid or sublingual gland, was smaller in patients with Sjögren's syndrome. CONCLUSIONS: The presence of multiple high-signal-intensity spots on an MR sialogram in the parotid gland should be considered the best diagnostic indicator for Sjögren's syndrome. The presence of spots, heterogeneity, and the change to smaller volumes in the submandibular gland were also helpful because of their high specificity, particularly in advanced cases.

Factors Associated with Increased Caregiver Burden of Informal Caregivers during the COVID-19 Pandemic in Japan.

This study's objective was to explore the association between various factors and the increased caregiver burden of informal caregivers during the COVID-19 pandemic. On February, 2021, 700 informal caregivers completed an online survey. We assessed the change in caregiver burden during the COVID-19 pandemic. Among all caregiver participants, 287 (41.0%) complained of an increased caregiver burden due to the COVID-19 pandemic. The factors associated with increased caregiver burden were depressive symptoms in caregivers [odds ratio (OR), 2.20; 95% confidence interval (CI), 1.50-3.23], dementia (OR, 2.48; 95%CI, 1.07-5.73) and low Barthel Index scores (OR, 2.01; 95%CI, 1.39-2.90) in care receivers, care days (OR, 1.09; 95%CI, 1.01-1.17) and times (OR, 1.06; 95%CI, 1.01-1.10), and use of home care service (OR, 1.46; 95%CI, 1.01-2.10) and visiting care service (OR, 1.71; 95%CI, 1.20-2.45). These findings suggest we need to pay attention to the physical and mental health of both the care receivers and caregivers.

Translocation of a calcium-permeable cation channel induced by insulin-like growth factor-I.

Calcium plays a critical part in the regulation of cell growth, and growth factors stimulate calcium entry into cells through calcium-permeable channels. However, the molecular nature and regulation of calcium-permeable channels are still unclear at present. Here we report the molecular characterization of a calcium-permeable cation channel that is regulated by insulin-like growth factor-I (IGF-I). This channel, which we name growth-factor-regulated channel (GRC), belongs to the TRP-channel family and localizes mainly to intracellular pools under basal conditions. Upon stimulation of cells by IGF-I, GRC translocates to the plasma membrane. Thus, IGF-I augments calcium entry through GRC by regulating trafficking of the channel.

Molecular identification of a eukaryotic, stretch-activated nonselective cation channel.

Calcium-permeable, stretch-activated nonselective cation (SA Cat) channels mediate cellular responses to mechanical stimuli. However, genes encoding such channels have not been identified in eukaryotes. The yeast MID1 gene product (Mid1) is required for calcium influx in the yeast Saccharomyces cerevisiae. Functional expression of Mid1 in Chinese hamster ovary cells conferred sensitivity to mechanical stress that resulted in increases in both calcium conductance and the concentration of cytosolic free calcium. These increases were dependent on the presence of extracellular calcium and were reduced by gadolinium, a blocker of SA Cat channels. Single-channel analyses with cell-attached patches revealed that Mid1 acts as a calcium-permeable, cation-selective stretch-activated channel with a conductance of 32 picosiemens at 150 millimolar cesium chloride in the pipette. Thus, Mid1 appears to be a eukaryotic, SA Cat channel.

Ambient C1- ions modify rat mesangial cell contraction by modulating cell inositol trisphosphate and Ca2+ via enhanced prostaglandin E2.

Our recent observation showed that angiotensin II (AII) and arginine vasopressin (AVP) stimulate Ca2+-activated Cl- conductance in mesangial cells. These data raise the possibility that mesangial cell function may be modulated by extracellular chloride concentration [( Cl-]o). The present study was undertaken to test this possibility using cultured rat mesangial cells. When the [Cl-]o was reduced to zero, the percentage of mesangial cells showing contraction responding to AII and AVP was decreased from 72 +/- 9 to 33 +/- 10% and from 60 +/- 4 to 24 +/- 11%, respectively. Ca2+ transients induced by AII and AVP, measured in mesangial cells loaded with Ca2+-sensitive photoprotein aequorin, were attenuated as [Cl-]o decreased. Also, when [Cl-]o decreased, inositol trisphosphate (IP3) levels of mesangial cells were suppressed, both in the presence and absence of AII or AVP. PGE2 production by mesangial cells increased when [Cl-]o decreased and the effects of ambient Cl- deprivation could be restored by addition of indomethacin to the Cl- -free medium. Moreover, PGE2 decreased mesangial cell contractility, Ca2+ transients, and IP3 production in response to AII and AVP. These data suggest that the decrease in [Cl-]o attenuates mesangial cell contraction by suppressing IP3 production and thus Ca2+ transients in response to AII and AVP through enhanced PGE2 production.

Activin A: an autocrine inhibitor of initiation of DNA synthesis in rat hepatocytes.

The present study was conducted to examine the effect of activin A on growth of rat hepatocytes. EGF induced a 10-fold increase in DNA synthesis as assessed by [3H]thymidine incorporation in cultured hepatocytes. When activin A was added together with EGF, DNA synthesis induced by EGF was markedly inhibited. Inhibition was detected at a concentration of 10(-10) M, and 5 x 10(-9) M activin A almost completely blocked EGF-mediated DNA synthesis. Similarly, activin A completely blocked DNA synthesis induced by hepatocyte growth factor/scatter factor. Activin A was capable of inhibiting EGF-mediated DNA synthesis, even when added 36 h after the addition of EGF. With the same time interval, TGF-beta also blocked EGF-induced DNA synthesis. Although both activin A and TGF-beta inhibited growth of hepatocytes in a similar manner, either activin A or TGF-beta did not compete with each other in their binding when assessed by competitive binding using an iodinated ligand. When hepatocytes were incubated with EGF, release of bioactivity of activin A into culture medium was detected after 48 h or later. Activity of activin A was released from parenchymal cells but not from nonparenchymal cells. mRNA for beta A subunit of activin was detected only slightly in unstimulated hepatocytes, but markedly increased at 48 h after the addition of EGF. To determine whether endogenously produced activin A affects DNA synthesis, we examined the effect of follistatin, an activin-binding protein that blocks the action of activin A. An addition of follistatin significantly enhanced EGF-induced DNA synthesis. Finally, in partial hepatectomized rat, expression of mRNA for beta A subunit in liver was markedly increased 24 h after the partial hepatectomy. These results indicate that activin A inhibits initiation of DNA synthesis in hepatocytes by acting on its own receptor and that activin A acts as an autocrine inhibitor of DNA synthesis in rat hepatocytes.

Betacellulin and activin A coordinately convert amylase-secreting pancreatic AR42J cells into insulin-secreting cells.

Rat pancreatic AR42J cells possess exocrine and neuroendocrine properties. Activin A induces morphological changes and converts them into neuron-like cells. In activin-treated cells, mRNA for pancreatic polypeptide (PP) but not that for either insulin or glucagon was detected by reverse transcription-PCR. About 25% of the cells were stained by anti-PP antibody. When AR42J cells were incubated with betacellulin, a small portion of the cells were stained positively with antiinsulin and anti-PP antibodies. The effect of betacellulin was dose dependent, being maximal at 2 nM. Approximately 4% of the cells became insulin positive at this concentration, and mRNAs for insulin and PP were detected. When AR42J cells were incubated with a combination of betacellulin and activin A, approximately 10% of the cells became insulin positive. Morphologically, the insulin-positive cells were composed of two types of cells: neuron-like and round-shaped cells. Immunoreactive PP was found in the latter type of cells. The mRNAs for insulin, PP, glucose transporter 2, and glucokinase, but not glucagon, were detected. Depolarizing concentration of potassium, tolbutamide, carbachol, and glucagon-like peptide-1 stimulated the release of immunoreactive insulin. These results indicate that betacellulin and activin A convert amylase-secreting AR42J cells into cells secreting insulin. AR42J cells provide a model system to study the formation of pancreatic endocrine cells.

The role of the activin-follistatin system in the developmental and regeneration processes of the kidney.

Regeneration processes in many tissues are modulated by various factors, which are involved in their organogenesis. Activin A, a member of the TGF-beta superfamily, inhibits branching tubulogenesis of the kidney in organ culture system as well as in in vitro tubulogenesis model. On the other hand, follistatin, an antagonist activin A, reverses the effect of activin A on kidney development, induces branching tubulogenesis, and also promotes tubular regeneration after ischemia/reperfusion injury by blocking the action of endogenous activin A. The activin-follistatin system is one of the important regulatory systems modulating developmental and regeneration processes of the kidneys.

Action of TMB-8 (8-(N,N-diethylamino)octyl-3,4,5-trimethoxybenzoate) on cytoplasmic free calcium in adrenal glomerulosa cell.

To clarify the action of 8-(N,N-diethylamino)octyl-3,4,5-trimethoxybenzoate (TMB-8) on cellular calcium handling, changes in cytoplasmic free calcium concentration ([Ca2+]c) were studied in adrenal glomerulosa cell with a calcium-sensitive photoprotein, aequorin. Results of our previous study demonstrate that 100 microM TMB-8 almost completely blocks aldosterone response to angiotensin II (Biochem. J. 232 (1985) 87-92). At 50 or 100 microM, TMB-8 decreased basal [Ca2+]c significantly; however, these doses of TMB-8 had little effect on an angiotensin-induced increase in [Ca2+]c. When angiotensin-induced calcium release from an intracellular pool(s) was assessed by measuring changes in [Ca2+]c in the presence of 1 microM extracellular Ca2+, 100 microM TMB-8 had little inhibitory effect on angiotensin-induced calcium release. A higher dose of TMB-8 (250 microM) slightly inhibited calcium release. Additionally, TMB-8 did not affect exogenous arachidonic acid-induced calcium release. In contrast, 50 microM TMB-8 markedly inhibited 8 mM potassium-induced increase in [Ca2+]c. These results indicate that a major action of TMB-8 on cellular calcium is an inhibition of calcium influx but not of calcium release. We suggest that TMB-8 should not be used as an 'inhibitor of calcium release'.

Evidence of cyclic AMP-independent action of glucagon on calcium mobilization in rat hepatocytes.

Glucagon increases the cytoplasmic free calcium concentration as measured by aequorin bioluminescence. It has been proposed by Wakelam et al. (Nature 323 (1986) 68-71) that low concentrations of glucagon mobilize calcium from an intracellular pool by causing polyphosphoinositide breakdown. To identify whether cyclic AMP mediates changes in the cytoplasmic free calcium concentration ([Ca2+]c) induced by glucagon, the effects of forskolin and exogenous cyclic AMP on [Ca2+]c were compared with that of glucagon in aequorin-loaded hepatocytes. Although the magnitudes of the [Ca2+]c responses to 250 microM forskolin and 1 mM 8-bromo cyclic AMP were identical to that of 5 nM glucagon, these two agents induced a more prolonged elevation of [Ca2+]c. Glucagon-induced elevation of [Ca2+]c was accompanied by a smaller increase in cyclic AMP than that induced by forskolin. When the cyclic AMP response to glucagon was potentiated by an inhibitor of phosphodiesterase, 3-isobutyl-1-methylxanthine, the glucagon-induced increase in [Ca2+]c was not affected. Conversely, when the cyclic AMP response to glucagon was reduced by pretreatment of the cells with angiotensin II, glucagon-induced changes in [Ca2+]c were rather enhanced. Furthermore, vasopressin potentiated glucagon-induced changes in [Ca2+]c despite the reduction of the cyclic AMP response to glucagon. In the presence of 1 microM extracellular calcium, angiotensin II did not enhance glucagon-induced changes in [Ca2+]c. These results suggest that at least part of the action of 5 nM glucagon on calcium mobilization is independent of cyclic AMP.

Granulosa cell luteinizing hormone receptor expression is modulated by ganglioside-specific ligands.

The ganglioside GM1 (Gal beta 1-->3GalNAc beta 1-->4[NeuAc alpha 2-->3] Gal beta 1-->4Glc beta 1-->1Cer) was synthesized during granulosa cell development in vitro, and the effect of the interaction between cell-surface GM1 and its ligands on the luteinizing hormone (LH) receptor expression was investigated. GM1 synthesis, demonstrated by metabolic labeling of glycosphingolipids with [3H]galactose and binding studies using the 125I-B-subunit of cholera toxin, a specific ligand for GM1, was increased in follicle-stimulating hormone (FSH)-treated granulosa cells. When granulosa cells were cultured for 72 h in a medium containing the B-subunit of cholera toxin, FSH-induced LH-receptor contents determined by measuring the binding of 125I-deglycosylated human chorionic gonadotropin to intact cells, was augmented. The stimulatory effect of the B-subunit was dependent on the FSH concentration and culture duration. The augmentation was observed after culture for 48 h, and marked increases were evident after 72 h, which coincided with an increase of the 125I-B-subunit binding capacity. Scatchard analysis of the LH-receptor binding indicated that treatment with the B-subunit increased the number of LH-binding sites (6580 sites/cell after treatment with 20 ng/ml FSH; 11,290 sites/cell after FSH plus 100 ng/ml B-subunit), but did not alter the binding affinity. A specific antibody against GM1 mimicked the stimulatory effect of the B-subunit. The augmentation was not accompanied by granulosa cell proliferation. These findings suggest that binding of exogenous or possible endogenous ligands to cell-surface GM1 produces signals and modulates the cellular behavior during granulosa cell development.

Studies on the effect of parathyroid hormone (1-84) on glucose output in the liver: comparison of effects in isolated hepatocytes and in perfused liver.

This study was conducted to determine the action of parathyroid hormone (1-84) (PTH(1-84)) on glucose output both in perfused liver and in isolated hepatocytes. In isolated rat hepatocytes, PTH(1-84) stimulated glucose output in a concentration-dependent manner. The action was detected at 10(-11) M and, at 10(-9) M, PTH produced its maximal effect. The magnitude of the maximal effect of PTH(1-84) was about 65% of that of phenylephrine. In contrast, PTH(1-84) had no effect on glucose output in perfused rat liver. Concentration of PTH(1-84) in effluent of perfused liver was less than that in the inflow. However, when the effluent obtained from liver perfused with 10 nM PTH(1-84) was added to isolated hepatocytes, a considerable amount of glucose was released, which was reversed by PTH(7-34), a competitive inhibitor of PTH receptor. These results indicate that PTH(1-84) increases glucose output in isolated hepatocytes but not in intact liver. It is suggested that the action of PTH(1-84) is blocked in intact liver by a yet unknown mechanism.

Assessment of the role of Ca2+ mobilization from intracellular pool(s), using dantrolene, in the glycogenolytic action of alpha-adrenergic stimulation in perfused rat liver.

To identify the role of Ca2+ mobilization from intracellular pool(s) in the action of alpha-adrenergic agonist, the effects of dantrolene on phenylephrine-induced glycogenolysis were investigated in perfused rat liver. Dantrolene (5 X 10(-5) M) inhibited both glycogenolysis and 45Ca efflux induced by 5 X 10(-7) M phenylephrine. The inhibition by dantrolene was observed in the presence and absence of perfusate calcium. In contrast, dantrolene did not inhibit glycogenolysis induced by glucagon. To confirm the specificity of dantrolene action on calcium release in liver, experiments were also carried out using isolated hepatocytes. Dantrolene did not affect phenylephrine-induced production of inositol 1,4,5-trisphosphate. The compound did inhibit a rise in cytoplasmic Ca2+ concentration induced by phenylephrine both in the presence and absence of extracellular Ca2+. Thus, these results suggest that calcium release from an intracellular pool is essential for the initiation of alpha-adrenergic stimulation of glycogenolysis in the perfused rat liver.

Regulation of the expression of follistatin in rat hepatocytes.

To elucidate the regulation of follistatin production in the liver, we studied changes in steady-state follistatin mRNA levels in cultured rat hepatocytes. Activin A stimulated follistatin mRNA levels in a time- and concentration-dependent manner. The stimulatory effect of activin A on follistatin mRNA was significant at 2 h, maximal at 6 h and declined thereafter. Incubating the cells with EGF increased follistatin mRNA levels at 48 h and later. The EGF-induced increase in follistatin mRNA was markedly inhibited by exogenous follistatin in the culture medium, which blocks the action of activin A synthesized in hepatocytes, suggesting that endogenous activin A at least partly mediated the effect of EGF. We also examined the effects of transforming growth factor-beta (TGF-beta), glucagon and alpha-adrenergic agonist, phenylephrine, on follistatin mRNA levels. TGF-beta increased the follistatin mRNA to levels similar to those caused by activin A. Phenylephrine and glucagon also increased follistatin mRNA levels but the effects were transient and weaker than those caused by activin A. Finally, follistatin mRNA levels were markedly increased in remnant liver 3 h after 70% hepatectomy. The mRNA remained elevated for up to 72 h. These results indicate that the expression of mRNA for follistatin is positively controlled by activin A, TGF-beta and other hormones or neurotransmitters. The stimulatory effect of EGF on follistatin mRNA is mediated by activin A released from hepatocytes.

Impaired differentiation of endocrine and exocrine cells of the pancreas in transgenic mouse expressing the truncated type II activin receptor.

Activin A is expressed in endocrine precursor cells of the fetal pancreatic anlage. To determine the physiological significance of activins in the pancreas, a transgenic mouse line expressing the truncated type II activin receptor under the control of beta-actin promoter was developed. Histological analyses of the pancreas revealed that the pancreatic islets of the transgenic mouse were small in size and were located mainly along the pancreatic ducts. Immunoreactive insulin was detected in islets, some acinar cells, and in some epithelial cells in the duct. In addition, there were abnormal endocrine cells outside the islets. The shape and the size of the endocrine cells varied and some of them were larger than islets. These cells expressed immunoreactive insulin and glucagon. In the exocrine portion, there were morphologically abnormal exocrine cells, which did not form a typical acinar structure. The cells lacked spatial polarity characteristics of acinar cells but expressed immunoreactive amylase, which was distributed diffusely in the cytoplasm. Plasma glucose concentration was normal in the transgenic mouse before and after the administration of glucose. The insulin content of the pancreas in transgenic and normal mice was nearly identical. These results suggest that activins or related ligands regulate the differentiation of the pancreatic endocrine and exocrine cells.

Changes in the expression of transcription factors in pancreatic AR42J cells during differentiation into insulin-producing cells.

Pancreatic AR42J cells possess both exocrine and neuroendocrine properties and convert to insulin-producing cells upon treatment with activin A and hepatocyte growth factor (HGF). We studied changes in the mRNA expression of various transcription factors during the course of differentiation. Among the transcription factors studied, expression levels of Pax4 and neurogenin3 changed significantly. These two factors were not detected in naive cells, whereas their mRNA levels were markedly increased after treatment with activin A and HGF. Thus, these two factors were induced by activin A. Transfection of Pax4 did not induce any changes in morphology or expression of pancreatic polypeptide (PP). Furthermore, introduction of antisense Pax4 did not affect the conversion into insulin-producing cells induced by activin A and HGF. In contrast, transfection of neurogenin3 induced morphological changes similar to those induced by activin A. In addition, transfection of neurogenin3 induced the expression of PP. Conversely, introduction of antisense neurogenin3 blocked the differentiation of AR42J cells induced by activin A and HGF. These results indicate that activin A regulates the expression of neurogenin3, which is critical for the differentiation of AR42J into endocrine cells.

Genes expressed during the differentiation of pancreatic AR42J cells into insulin-secreting cells.

Pancreatic AR42J cells have the feature of pluripotency of the common precursor cells of the pancreas. Dexamethasone (Dx) converts them to exocrine cells, whereas activin A (Act) converts them into endocrine cells expressing pancreatic polypeptide. A combination of Act and betacellulin (BTC) converts them further into insulin-secreting cells. The present study identifies some of the genes involved in the process of differentiation that is induced by these factors, using the mRNA differential display and screening of the cDNA expression array. The expression levels of 7 genes were increased by Act alone, and a combination of Act and BTC increased the expression of 25 more genes. Of these, 16 represented known genes or homologues of genes characterized previously. Nine of the identified genes were unrelated to any other sequences in the database. An inhibitor of the mitogen-activated protein kinase pathway, PD098059, which blocks the differentiation into insulin-secreting cells, inhibited the expression of 18 of the 25 genes, suggesting that the proteins encoded by these genes are associated with the differentiation into insulin-producing cells. These include known genes encoding extracellular signaling molecules, such as parathyroid hormone-related peptide, cytoskeletal proteins, and intracellular signaling molecules. Identification and characterization of these differentially expressed genes should help to clarify the molecular mechanism of differentiation of pancreatic cells and the gene products that enable the beta-cells to produce insulin.

Upregulatory expression of furin and transforming growth factor-beta by fluid shear stress in vascular endothelial cells.

Furin, a yeast Kex2-family endoprotease, converts many vasoregulatory propeptides, including pro-transforming growth factor (TGF)-beta to their mature forms. We examined whether furin expression is regulated by shear stress in vivo and in vitro. When an arteriovenous shunt was placed between the carotid artery and external jugular vein in rabbits, furin and TGF-beta were highly expressed in shear stress-loaded endothelial cells. Exposure of bovine aortic endothelial cells in culture to shear stress induced furin and TGF-beta expression in a similar manner. Molecular analysis of furin expression in bovine aortic endothelial cells revealed that shear stress increases the furin gene expression at transcriptional levels. Furthermore, TGF-beta itself increased the furin mRNA levels. Shear-mediated furin expression was partly mediated by TGF-beta because shear-induced furin mRNA levels were considerably decreased by overexpression of the truncated form of the TGF-beta type II receptor. Likewise, blockade of furin activity by a furin inhibitor significantly decreased the endothelial production of mature TGF-beta. Taken together, the results indicate that furin expression is induced and maintained by a coordination of shear stress and TGF-beta. Increased furin expression may facilitate the formation of mature TGF-beta, resulting in the enhanced effects of TGF-beta on endothelial cells and vascular smooth muscle cells in the vasculature.

Inhibition of proliferation of MCF-7 breast cancer cells by a blocker of Ca(2+)-permeable channel.

In MCF-7 breast cancer cells, insulin-like growth factor-1 (IGF-1) increased the calcium-permeability of the cells by activating a voltage-independent calcium-permeable channel. IGF-1 also induced oscillatory elevation of cytoplasmic free calcium concentration in these cells. An anti-allergic compound, tranilast, reduced the calcium-permeability augmented by IGF-1 in a dose-dependent manner and blocked the oscillatory elevation of cytoplasmic free calcium concentration. Tranilast did not affect early intracellular signals activated by IGF-1, including receptor autophosphorylation, activations of Ras, mitogen-activated protein kinase and phosphatidylinositol 3-kinase. Tranilast inhibited increases in [3H]-thymidine incorporation, DNA content and cell number induced by IGF-1. The ID50 for [3H]-thymidine incorporation and DNA content were about 10 microM. The inhibitory effect of tranilast was reversible, and cell viability was not affected. Treatment with tranilast increased the number of cells in the G1 phase suggesting that this compound induced G1 arrest. Tranilast also reduced the phosphorylation of the retinoblastoma protein. These results indicate that tranilast inhibits the IGF-1-induced cell growth in MCF-7 cells by blocking calcium entry.

Possible role of phospholipase A2 action and arachidonic acid metabolism in angiotensin II-mediated aldosterone secretion.

When [3H]arachidonic acid-labeled calf adrenal glomerulosa cells are stimulated by angiotensin II (AII), free [3H]arachidonic acid is released. AII treatment significantly decreases radioactivity in phosphatidylinositol but not in other phospholipids. Inhibitors of phospholipase A2 (PL-A2) activity, quinacrine and p-bromophenacyl bromide, inhibit AII-stimulated aldosterone secretion from glomerulosa cells in a dose-dependent manner. The effect of these inhibitors is irreversible when used at high concentration, but not when employed at lower concentration. Exogenous PL-A2 as well as arachidonic acid stimulates both radiocalcium efflux and aldosterone secretion. Unlike AII, stimulation of aldosterone secretion by PL-A2 is only transient. Radiocalcium efflux induced by PL-A2 is greater than that induced by AII and is not inhibited by either nitrendipine or dantrolene. Pretreatment with PL-A2 abolishes the radiocalcium efflux response to subsequent AII, whereas AII pretreatment does not abolish the subsequent PL-A2-mediated radiocalcium efflux response. The aldosterone secretory response to AII is not affected by 0.3 microM indomethacin but is inhibited by either of three compounds which inhibit lipoxygenase activity; 5,8,11,14-eicosatetraynoic acid, BW755c, or caffeic acid. In a static incubation system, AII-stimulated aldosterone secretion is inhibited 40-50% by any of these lipoxygenase inhibitors. In a perifusion system, BW755c partially inhibits only the sustained phase of AII-stimulated aldosterone secretion. However, BW755c has no effect on the secretion of aldosterone in response to combined A23187 plus 12-O-tetradecanoyl-phorbol-13-acetate. These results suggest that PL-A2 action is not obligatory in AII-induced aldosterone secretion and that lipoxygenase, but not cyclooxygenase, products of arachidonic acid metabolism may play a role in AII action as positive feed forward mediators.